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UBC Theses and Dissertations

Learned taste aversions by rats to compound stimuli Wilson, C. Scott 1977

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LEARNED TASTE AVERSIONS BY RATS TO COMPOUND STIMULI by C. SCOTT WILSON B.A., Eas t e r n Washington State C o l l e g e , 1969 M. A., Eastern Washington State C o l l e g e , 1971 A THESIS SUBMITTED IN PARTIAL FULFILMENT OF THE REQUIREMENTS FOR THE DEGREE OF DOCTOR OF PHILOSOPHY i n the Department of Psychology Wa accept t h i s t h e s i s as conforming t o the r e q u i r e d standard THE UNIVERSITY OF BRITISH COLUMBIA August, 1976 (§) C . S c o t t Wilson 1977 i In presenting th i s thesis in pa r t i a l fu l f i lment of the requirements for an advanced degree at the Univers i ty of B r i t i s h Columbia, I agree that the L ibrary shal l make it f ree ly ava i lab le for reference and study. I fur ther agree that permission for extensive copying of th i s thesis for scho lar ly purposes may be granted by the Head of my Department or by his representat ives. It is understood that copying or pub l i ca t ion of this thes is for f inanc ia l gain sha l l not be allowed without my written permission. Department of The Univers i ty of B r i t i s h Columbia 2 0 7 5 W e s b r o o k P l a c e V a n c o u v e r , C a n a d a V 6 T 1 W 5 i ABSTRACT Learned Taste Aversions by Rats t o Compound S t i m u l i by C. Scott Wilson Learned t a s t e a v e r s i o n s occur i f water-deprived r a t s ' I n g e s t i o n of a novel f l a v o r e d s o l u t i o n i s followed by t o x i c o s i s . Since l i t t l e i s known about l e a r n e d a v e r s i o n s to mixtures of two d i s t i n c t f l a v o r s , the present s e r i e s of s i x major experiments was performed. In Experiment I compounds of two f l a v o r s were p a i r e d with L i C l t o x i c o s i s . During subseguent t e s t p e r i o d s , i n which the compound and the i n d i v i d u a l f l a v o r s were presented, the r a t s avoided the component f l a v o r s as w e l l as the compound. The compound was g e n e r a l l y avoided more than i n d i v i d u a l t a s t e elements. In Experiment I I two f l a v o r s were s e p a r a t e l y p a i r e d with t o x i c o s i s . During subsequent t e s t p e r i o d s , the r a t s avoided the compounds of the f l a v o r s as well as the i n d i v i d u a l f l a v o r s . Some evidence of s t r o n g e r avoidance of the compound was found. In Experiment I I I compounds of two f l a v o r s , one f a m i l i a r and one novel to the r a t s , were f o l l o w e d by t o x i c o s i s . The r a t s avoided the compound and the novel f l a v o r , but showed much l e s s avoidance of the f a m i l i a r f l a v o r during subsequent t e s t s . Avoidance of the n o v e l s o l u t i o n was g r e a t e r than when put i n compound with another novel f l u i d and followed by t o x i c o s i s . In Experiment IV one f l a v o r was e x p l i c i t l y p a i r e d , while a second i i f l a v o r was e x p l i c i t l y not p a i r e d with t o x i c o s i s . During t e s t i n g the r a t s avoided the p a i r e d but not the unpaired t l a v o r . The compound of the two f l a v o r s was consumed i n q u a n t i t i e s i n t e r m e d i a t e between the two i n d i v i d u a l f l a v o r s . In Experiment V the c o n c e n t r a t i o n of one f l a v o r of the compound was i n c r e a s e d . During t e s t s , which f o l l o w e d p a i r i n g of the compound with t o x i c o s i s , a s t r o n g e r a v e r s i o n to the more concentrated f l a v o r was observed with some f l a v o r s but not others. In Experiment VI one f l a v o r was f o l l o w e d by t o x i c o s i s p r i o r to the compound of t h i s f l a v o r and another being fo] lowed by p o i s o n i n g . Tiie r a t s avoided both f l a v o r s as we l l as the compound d u r i a q subsequent t e s t s . With the p o s s i b l e exception of the r e s u l t s of Experiment VI, the r e s u l t s of these experiments are q u i t e s i m i l a r t o the r e s u l t s obtained i n more t r a d i t i o n a l l e a r n i n g paradigms. A majori t y of the e f f e c t s found are accounted f o r by contemporary l e a r n i n g t h e o r i e s . Donald H. W i l k i e i i i TABLE OF CONTENTS INTRODUCTION 1 Learned Taste Aversions 1 CS-UCS I n t e r v a l i n Taste Aversion Learning 1 Cue-Consequence A s s o c i a b i l i t y 2 P r i m i t i v e Systems A n a l y s i s of Learned Taste A v e r s i o n s .. 7 Currant Status of Taste Aversion Learning ............. 9 A S t r a t e g y f o r Dea l i n g with P o s s i b l e Unique Aspects of Taste Aversion Learning 9 Compound Stimulus C o n t r o l 10 Purpose of the Present Research 13 GENERAL METHOD 15 O r g a n i z a t i o n of Experiments 15 Subjects 15 Procedure 15 EXPERIMENT IA: Compound C o n d i t i o n i n g with Preexposure: C o n t r o l by Elements 18 Method 19 Subjects 19 Procedure . 19 Data P r e s e n t a t i o n and A n a l y s i s 21 R e s u l t s 22 Summary o f Results 30 EXPERIMENT IB: Compound C o n d i t i o n i n g without Preexposure: C o n t r o l by Elements 32 Method 3 2 i v Subjects ,. . 32 Procedure 32 Data P r e s e n t a t i o n and A n a l y s i s 3 ^ R e s u l t s 3ir Summary of Resu l t s 38 D i s c u s s i o n 38 EXPERIMENT I I ; Compounding S e p a r a t e l y Conditioned Taste Elements 42 Method 42 Subjects 42 Procedure 43 Data P r e s e n t a t i o n and A n a l y s i s 4 ^ R e s u l t s 45 Summary of Resu l t s 51 D i s c u s s i o n 52 EXPERIMENT I I I : Compound C o n d i t i o n i n g with F a m i l i a r and U n f a m i l i a r Taste Elements 59 Method 59 S u b j e c t s 59 Procedure 59 Data P r e s e n t a t i o n and A n a l y s i s 61 R e s u l t s 61 Summary of R e s u l t s 61L D i s c u s s i o n 6£ EXPERIMENT IV: Compound C o n d i t i o n i n g with F a m i l i a r (Safe) and Novel Tastes ., 68 Method 68 V Subjects 68 Procedure 69 Data P r e s e n t a t i o n and A n a l y s i s 70 R e s u l t s 70 Summary of Results 72 D i s c u s s i o n 7_L EXPERIMENT V: Overshadowing i n Taste Compounds 81 Method 82 Subjects 82 Procedure 83 Data P r e s e n t a t i o n and A n a l y s i s 85? R e s u l t s 85 Summary o f Re s u l t s 89 D i s c u s s i o n 89 EXPERIMENT VI: B l o c k i n g : C o n d i t i o n i n g to the Elements of a Compound Taste Stimulus A f t e r P r i o r C o n d i t i o n i n g t o One Element 9f Method 99 Subjects 9 9 Procedure 99 Data P r e s e n t a t i o n and A n a l y s i s 103 R e s u l t s 103 Summary o f Resu l t s 113 D i s c u s s i o n 113 GENERAL SUMMARY AND DISCUSSION 123 v i REFERENCES 127 APPENDIX A 138 LIST OF TABLES Table 1. Summary of procedure f o r each group, showing t a s t e s o l u t i o n s presented i n each of the t h r e e major phases of Experiment IA 20 Table 2 . Summary of procedure f o r aach group, showing t a s t e s o l u t i o n s presented i n each of the two major phases of Experiment IB 33 Table 3 . Summary of procedure f o r each group, showing t a s t e s o l u t i o n s presented i n each of the two major phases of Experiment I I 43 Table 4. Summary of procedure f o r each group, showing t a s t e s o l u t i o n s presented i n each of the three major phases of Experiment T I I 60 Table 5 . Summary of procedure, showing t a s t e s o l u t i o n s presented i n each of the three major phases of Experiment IV 69 Table 6 Summary of procedure f o r each qroup, showing t a s t e s o l u t i o n s presented i n each of the two major phases of Experiment V 83 Table 7 . Summary of procedure f o r each group, showing t a s t e s o l u t i o n s presented i n each of the three major phases of Experiment VI 101 v i i i LIST OF FIGURES Figu r e 1-A. B a s e l i n e preexposure, c o n d i t i o n i n g , and e x t i n c t i o n f l u i d intake f o r Group 1 .. . . 24 Figure 1-B. B a s e l i n e preexposure, c o n d i t i o n i n g , aud e x t i n c t i o n f l u i d i n t a k e f o r Group 2 26 Figure 1 - c . B a s e l i n e preexposure, c o n d i t i o n i n g , and e x t i n c t i o n f l u i d i n t a k e f o r Group 3 28 Figure 1-D. B a s e l i n e preexposure, c o n d i t i o n i n g , and e x t i n c t i o n f l u i d i n t a k e f o r Group 4 29 Fig u r e 1-E. C o n d i t i o n i n g and e x t i n c t i o n f l u i d i n t a k e f o r a l l groups of Experiment IB 35 F i g u r e 2-A. C o n d i t i o n i n g and e x t i n c t i o n f l u i d i n t a k e i o r Group 1 46 Figure 2-B. C o n d i t i o n i n g and e x t i n c t i o n f l u i d i n t a k e f o r Group 2 48 F i g u r e 2-C. C o n d i t i o n i n g and e x t i n c t i o n f l u i d intaice f o r Group 3 49 F i g u r e 2-D. C o n d i t i o n i n g and e x t i n c t i o n f l u i d i n t a k e f o r Group 4 50 Figure- 3-A. Preexposure, c o n d i t i o n i n g , and e x t i n c t i o n f l u i d i n t a k e f o r Group 1 62 F i g u r e 3-B. Preexposure, c o n d i t i o n i n g , and e x t i n c t i o n f l u i d i n t a k e f o r Group 2 6I4. F i g u r e 4-A. Preexposure, c o n d i t i o n i n g , and e x t i n c t i o n f l u i d i n t a k e In C o n d i t i o n 1 72 Fig u r e 4-B. D i f f e r e n t i a l c o n d i t i o n i n g and e x t i n c t i o n t_.uid i n t a k e i n C o n d i t i o n 2 73 Figure 5-A. C o n d i t i o n i n g and e x t i n c t i o n f l u i d i n t a k e f o r Group 1 86 Figure 5-8. D i f f e r e n t i a l c o n d i t i o n i n g and e x t i n c t i o n f l u i d i n t a k e f o r Group 2 8? F i g u r e 5-C. C o n d i t i o n i n g and e x t i n c t i o n f l u i d i n t a k e i o r Group 3 88 Figure 6-A. C o n d i t i o n i n g and e x t i n c t i o n f l u i d i n t a k e f o r Group 1 10li Figure 6-B. C o n d i t i o n i n g and e x t i n c t i o n f l u i d i n t a k e i o r i x Group 2 10£ Figure 6-C. C o n d i t i o n i n g and e x t i n c t i o n f l u i d i n t a k e f o r Group 3 107 F i g u r e 6-D. Preexposure, c o n d i t i o n i n g , and e x t i n c t i o n f l u i d i n t a k e f o r Group 4 108 Figure 6-E. C o n d i t i o n i n g and e x t i n c t i o n f l u i d i n t a k e f o r Group 5 . . . 109 F i g u r e 6-F. C o n d i t i o n i n g and e x t i n c t i o n f l u i d i n t a k e f o r Group 6 111 Figure 6-G. Preexposure, c o n d i t i o n i n g , and e x t i n c t i o n f l u i d i n t a k e f o r Group 7 , . . 112 JC iCKNOWLEDGEMENTS I would e s p e c i a l l y l i k e to thank Don Milkxe and Bod Wong f o r t h e i r a s s i s t a n c e with the present r e s e a r c h . I would a l s o l i k e t o thank C h r i s F i b i g e r and Richard Teese f o r t h e i r h e l p f u l comments reg a r d i n g the present t h e s i s . T h i s r e s e a r c h was supported i n pa r t by N a t i o n a l Research C o u n c i l of Canada grants t o D. «. s i l k i e and fi. fang. 1 ._.eajrn«d Taste Aversions The t y p i c a l procedure f o r producing l e a r n e d t a s t e a v e r s i o n s i n r a t s i n v o l v e s p a i r i n g a n o v e l t a s t e (e.g., s a l i n e ) with acute i n t e r o c e p t i v e malaise (e.£. , the g a s t r o i n t e s t i n a l upset f o l l o w i n g i n j e c t i o n of s u b l e t h a l doses of L i d ) . The r e s u l t of such p a i r i n g i s a dramatic decrease i n consumption of the f l u i d when i t i s next presented s e v e r a l days l a t e r . G a r c i a , Hawkins, S E u s i n i a k (1974) pointed out s e v e r a l d i f f e r e n c e s between t a s t e a v e r s i o n l e a r n i n g and l e a r n i n g i n more t r a d i t i o n a l cue-conseguence procedures- T r a d i t i o n a l cue avoidance l e a r n i n g u s u a l l y i n v o l v e s v i s u a l or a u d i t o r y c o n d i t i o n e d s t i m u l i (CS) such as l i g h t s , buzzers, and tones, p a i r e d with a v e r s i v e e x t e r o c e p t i v e unconditioned s t i m u l i (UCS) such as e l e c t r i c shock. For a t a s t e a v e r s i o n to be c o n d i t i o n e d t h e r e must be an a s s o c i a t i o n between the gustatory CS and the i n t e r o c e p t i v e UCS. G a r c i a et a l . (1974) argue that t h i s a s s o c i a t i o n has c e r t a i n unigue g u a l i t i e s which d i f f e r e n t i a t e i t from more t r a d i t i o n a l cue-conseguence l e a r n i n g . The two most s a l i e n t are the occurrence of l e a r n i n g d e s p i t e very long CS-UCS i n t e r v a l s {Garcia, E r v i n , & K o e l l i n g , 1966), and the apparent ease with which t a s t e s and i l l n e s s e s are a s s o c i a t e d (Garcia & K o e l l i n g , 1 966). CS-UCS I n t e r v a l i n Taste Aversion Learning Taste a v e r s i o n l e a r n i n g i s a f f e c t e d by parametric 2 manipulations of the CS-UCS i n t e r v a l i n ways s i m i l a r t o those found i n more t r a d i t i o n a l c o n d i t i o n i n g procedures. However, although the degree of c o n d i t i o n i n g decreases with i n c r e a s e s i n the CS-DCS i n t e r v a l , the time span i n v o l v e d i s c o n s i d e r a b l y l o n g e r than t h a t u s u a l l y assumed i n t r a d i t i o n a l l e a r n i n g f o r m u l a t i o n s (Kimble, 1967). The l e n g t h of time between g u s t a t o r y cue and subsequent induced i l l n e s s has o f t e n been s e v e r a l hours. T r a d i t i o n a l cue-consequence l e a r n i n g o f t e n f a i l s to occur with i n t e r v a l s of more than a few seconds. Becent work by L e t t (1973, 1975), however, suggests t h a t r e l a t i v e l y long cue-conseguence i n t e r v a l l e a r n i n g i s p o s s i b l e w i t h i n more t r a d i t i o n a l c o n d i t i o n i n g paradigms. L e t t ' s experiments i n v o l v e a delayed reinforcement procedure. In one experiment (1973) food deprived r a t s were rewarded f o r a p o s i t i o n a l response i n a T-maze. Unlike i n e a r l i e r experiments, the r a t was immediately removed to a temporary holding cage f o r the delay i n t e r v a l which f o l l o w e d a r i g h t - o r l e f t - a r m c h o i c e . The r a t was returned to the s t a r t area at the end of the delay and fed i f the p r e v i o u s response was c o r r e c t . L e t t ' s r a t s have l e a r n e d with d e l a y s between c h o i c e and food reinforcement of up to 1 hour. This i s a formidable delay when compared with t r a d i t i o n a l f o r m u l a t i o n s of e f f e c t i v e cue-consequence time r e l a t i o n s . Cue-Consequence Assoc l a b i l i t y . The d i f f e r e n c e between t r a d i t i o n a l cue-consequence l e a r n i n g and t a s t e a v e r s i o n l e a r n i n g s t r e s s e d by G a r c i a et a l . (1974) concerns the cue-consequence p a i r s that most e a s i l y e n t e r i n t o 3 a s s o c i a t i o n s . G a r c i a et a l . maintain t h a t g u s t a t o r y cues and s i c k n e s s "go t o g e t h e r " . T h i s i s s i m i l a r to Thorndike's (189 8) concept of "belongingness" and Seligman's (1973) concept of "preparedness"- G a r c i a et a l . (1974) c i t e c o n s i d e r a b l e evidence t h a t s t r o n g l y supports t h e view of p r e f e r e n t i a l g u s t a t o r y -malaise a s s o c i a b i l i t y (Rozin, 1969; G a r c i a & K o e l l i n g , 1966, 1967; G a r c i a , ficGowan & Green, 1972; Green, Bouzos, & S a c h l i n , 1972; Domjan £ Wilson, 1972a; G a r c i a , McGOwan, E r v i n & K o e l l i n g , 1968; Green & G a r c i a , 1971; Green, Holmstrom, & Wollman, 1974; G a r c i a & E r v i n , 1968). The evidence shows t h a t g u s t a t o r y cues are more e a s i l y a s s o c i a t e d with subsequent i l l n e s s i n the r a t than are d i s t i n c t i v e cues such as f l a s h i n g l i g h t s , buzzers, and c l i c k s . G a r c i a & K o e l l i n g (1966), i n a now c l a s s i c study, demonstrated t h i s apparent d i f f e r e n t i a l cue-consequence a s s o c i a b i l i t y . They p a i r e d a compound s t i m u l u s c o n s i s t i n g of " b r i g h t - n o i s y - t a s t y " water with X - r a d i a t i o n or L i C l p o i s o n i n q . A l i c k to the d r i n k i n g spout was f o l l o w e d by a f l a s h i n g l i g h t , a c l i c k i n g sound, and, of course, the t a s t e of the f l a v o r ( e i t h e r 0.1% s a c c h a r i n , or 1.0% NaCl). F o l l o w i n g a c q u i s i t i o n , d e f i n e d as suppressed d r i n k i n g of the compound CS, t e s t s f o r c o n t r o l by the component elements were admi n i s t e r e d by p r e s e n t i n g the component s t i m u l i . During the t e s t s the r a t s drank l i t t l e of the t a s t y water when i t was presented alone- However, there was no decrease i n consumption of the b r i g h t - n o i s y u n f l a v o r e d water. G a r c i a & K o e l l i n g (1967) , i n another study, found s i m i l a r r e s u l t s - They used a compound s t i m u l u s c o n s i s t i n g of a g u s t a t o r y element ( L i C l ) , and a v i s u a l - a u d i t o r y - t a c t u a l element. They found, a f t e r s e v e r a l CS-UCS p a i r i n g s , t h a t c o n t r o l was demonstrated on l y by the t a s t e of NaCl ( s i m i l a r i n t a s t e to L i C l a c c o r d i n g t o E r i c k s o n , Doetsch, & M a r s h a l l , 1966, and Nachman, 1 963). No i n t a k e s u p p r e s s i o n o c c u r r e d i n the presence of the v i s u a l - a u d i t o r y - t a c t u a l s t i m u l i . In f a c t , they p o i n t out t h a t the animals showed no avoidance r e a c t i o n to the compartment where the v i s u a l - a u d i t o r y - t a c t u a l s t i m u l i were l o c a t e d . T h i s i s i n c o n t r a s t to the " f e a r r e a c t i o n " u s u a l l y noted to the t e s t compartment when e l e c t r i c shock s e r v e s as the a v e r s i v e s t i m u l u s . One c o u l d argue that the simultaneous presence of both t a s t e cues and other environmental cues ( f l a s h i n g l i g h t s , etc.) m i t i g a t e d a g a i n s t c e r t a i n cues e n t e r i n g a s s o c i a t i o n s , i . e . , an overshadowing e f f e c t (Pavlov, 1927). Overshadowing r e f e r s t o the gr e a t e r c o n t r o l of responding by one element of a s t i m u l u s compound r e l a t i v e to another element when no p r i o r c o n d i t i o n i n g h i s t o r y with e i t h e r element can be assumed. For an overshadowing i n t e r p r e t a t i o n t o be v a l i d one would have to show th a t the overshadowed cues were e a s i l y c o n d i t i o n a b l e when presented alon e . Arguing a g a i n s t such an overshadowing i n t e r p r e t a t i o n i s G a r c i a S K o e l l i n g ' s (1967) work showing t h a t a d i s t i n c t i v e compartment p a i r e d independently with nausea-producing apomorphine h y d r o c h l o r i d e i n j e c t i o n s f a i l e d t o c o n t r o l any r e d u c t i o n i n f l u i d i n t a k e . G a r c i a , Kimeldorf, S Hunt (1961) a l s o r e p o r t e d g r e a t d i f f i c u l t y i n using X - r a d i a t i o n to o b t a i n avoidance o f a d i s t i n c t i v e v i s u a l - t a c t u a l CS. Other experiments have shown t h a t i t i s d i f f i c u l t to 5 produce taste aversions by pairing a gustatory cue with a consequence such as shock- Garcia S Koelling (1966) followed oright-noisy-tasty water with shock. The test r e s u l t s c l e a r l y showed that while the bright-noisy CS element suppressed drinking, taste alone did not-However, despite the apparently s o l i d evidence supporting the d i f f e r e n t i a l cue-consequenca a s s o c i a b i l i t y p o s i t i o n , i t has not gone unchallenged. Rozin (1969) has questioned the c^e-consequence a s s o c i a b i l i t y notion by demonstratinq rapid avoidance learning by a rat to a position and type of container when followed by immediate sickness (but not by sickness 30 min l a t e r ) . Others have recently joined Rozin i n questioning the d i f f i c u l t y of conditioning the avoidance of exteroceptive s t i m u l i by pairing them with toxi c o s i s (Best, Best, & Mickley, 1973; M i t c h e l l , Kirschbaum, S Perry, 1975; Morrison S C o l l y e r , 1974). Best, et a l . (1973) reported that r a t s , injected with 15 mg/kg apomorphine immediately after a 2-min period i n a black compartment, spent s i g n i f i c a n t l y less time i n the compartment on l a t e r testing than appropriate controls- If a compound stimulus of a black compartment and f l u i d (water or saccharin) was used, a s i g n i f i c a n t attenuation of the black compartment avoidance reaction occurred- However, the rats s t i l l avoided the black compartment- Apparently the presence of the f l u i d i n t e r f e r e d with conditioning to the black compartment. A related f i n d i n g was reported by M i t c h e l l , et a l , - (1975). They accustomed rats to the test s i t u a t i o n for either 10 or 25 aays prior to conditioning. Then they introduced a novel complex 6 of s t i m u l i composed of a d i f f e r e n t food c o n t a i n e r i n a d i f f e r e n t p o s i t i o n , as well as c o n t a i n i n g d i f f e r e n t t e x t u r e d but the same f l a v o r e d food (0.5 cm diameter ground r a t chow i n s t e a d of 1.5 cm). F o l l o w i n g 30 min access to t h i s novel CS, L i C l was i n j e c t e d . The 25 day h a b i t u a t i o n group c l e a r l y avoided the CS complex (consumed l e s s ) , while the 10 day h a b i t u a t i o n group d i d not. T h i s powerful e f f e c t o c c u r r e d with only two C S - t o x i c o s i s p a i r i n g s r a t h e r than the s e v e r a l r e q u i r e d of previous r e s e a r c h . The authors concluded t h a t an important f a c t o r concerning CS-t o x i c o s i s c o n d i t i o n i n g appears to be how w e l l the CS stands out from the other environmental cues. Obviously the CS w i l l stand out i n d i r e c t r e l a t i o n to how long the r a t has been exposed to the c o n d i t i o n i n g s i t u a t i o n p r i o r to i n t r o d u c t i o n of the novel CS (see Lubow, R i f k i n 6 Alek, 1976 f o r a f u r t h e r d i s c u s s i o n of t h i s point) . The po i n t of G a r c i a et a l . (1974) p o i n t concerning the d i f f i c u l t y of a s s o c i a t i n g t a s t e cues and e x t e r o c e p t i v e shock has a l s o r e c e n t l y been questioned. Krane & Wagner (1975) found that r a t s subsequently avoided a 0-7% s a c c h a r i n s o l u t i o n a f t e r d r i n k i n g i t was fo l l o w e d by shock 0.5 or 3.5 minutes l a t e r . Krane and Wagner suggest t h a t the apparent " q u a l i t a t i v e " d i f f e r e n c e between g u s t a t o r y - t o x i c o s i s c o n d i t i o n i n g and other cue-consequence l e a r n i n g might be r e s o l v a b l e i n a g u a n t i t a t i v e f a s h i o n . They p o i n t out that the CSs and OCSs used i n t a s t e a v e r s i o n as d i s t i n c t from other c o n d i t i o n i n g procedures d i f f e r i n many ways ( i n t e n s i t y , p e r i o d i c i t y , e t c . ) . I t i s thus premature t o accept q u a l i t a t i v e d i f f e r e n c e s i n cue-consequence a s s o c i a b i l i t y when i t may be oth e r stimulus-conseguence i 7 parameters t h a t are r e s p o n s i b l e f o r the ease of a s s o c i a b i l i t y . A s i m i l a r s uggestion has been made by others as w e l l (Testa, 1974, 1975; Bitterman, 1975, 1976). Regardless of the f i n a l r e s o l u t i o n of the cue-conseguence s p e c i f i c i t y n o t i o n , i t s uniqueness t o t a s t e a v e r s i o n l e a r n i n g i s q u e s t i o n a b l e . Recently Foree & LoLordo (1973, 1975) have demonstrated s p e c i f i c i t y of cue-consequence a s s o c i a b i l i t y u s ing the v i s u a l and a u d i t o r y systems of the pigeon. Pigeons were t r a i n e d to depress a t r e a d l e to avoid shock o r o b t a i n food i n the presence of a compound s t i m u l u s composed of a tone and a red l i g h t - For pigeons t r a i n e d t o avoid shock, c o n t r o l was exerted by the tone, but not the red l i g h t - However, responding by other pigeons t r a i n e d with the same compound but on an a p p e t i t i v e t a s k was c o n t r o l l e d by the red l i g h t , but not the tone (see a l s o LoLordo & Furrow, 1976). Thus, s e l e c t i v e s t i m u l u s c o n t r o l on the b a s i s of cue-conseguence r e l a t i o n s has been demonstrated even i n more " t r a d i t i o n a l " cue-consequence procedures. This does not d e t r a c t from the p o s s i b l e uniqueness of t a s t e - s i c k n e s s a s s o c i a t i o n s , but does show that other systems have s i m i l a r c h a r a c t e r i s t i c s . P r i m i t i v e Systems A n a l y s i s of Learned Taste A v e r s i o n s Ka l a t & Rozin (1972) have suggested t h a t t a s t e a v e r s i o n l e a r n i n g may be n e u r o l o g i c a l l y "more p r i m i t i v e " i n comparison t o other cue-consequence l e a r n i n g - Support f o r such a view comes from the known d u a l i t y of n e u r a l c o n t r o l of e x t e r n a l and i n t e r n a l a f f e r e n t i n p u t s i n t o the c e n t r a l nervous system ( H e r r i c k , 1961; Morest, 1967)- G a r c i a , HcGowan & Green (1972) 8 p o i n t out that a f f e r e n t neurons from both g u s t a t o r y and v i s c e r a l r e c e p t o r s p r o j e c t to the nucleus of the f a s c i c u l u s s o l i t a r i u s i n the b r a i n stem, thus presumably f a c i l i t a t i n g a t a s t e - i l l n e s s a s s o c i a t i o n a t a r e l a t i v e l y low n e u r a l l e v e l - One s u p p o r t i n g p i e c e of evidence i s the r e s u l t s of R o l l & smith (1972). They found i t p o s s i b l e to o b t a i n a t a s t e a v e r s i o n i n r a t s rendered unconscious d u r i n g the UCS p r e s e n t a t i o n and subseguent i l l n e s s . Suresova & Bures (1974) have r e p o r t e d s i m i l a r r e s u l t s f o l l o w i n g the a p p l i c a t i o n of KC1 t o the c o r t e x of r a t s ( c o r t i c a l spreading d e p r e s s i o n procedure). However, c o n d i t i o n i n g of an "unconscious" p r e p a r a t i o n has a l s o apparently been demonstrated i n other more common cue-conseguence l e a r n i n g procedures (Horridge, 1962; Chopin & Buerger, 1975; Buerger S Fennessy, 1971; F a r e ! & Buerger, 1972). I t should be noted that Church (1976) has r e c e n t l y guestioned the v a l i d i t y of these experiments. Arguing f o r the p o t e n t i a l complexity of t a s t e a v e r s i o n l e a r n i n g i s the r e c e n t work by Buresova & Bures (1973), showing th a t the i n t a c t c o r t e x i s necessary f o r t a s t e a v e r s i o n l e a r n i n g . Buresova S Bures (1973) showed that a c o n d i t i o n e d s a c c h a r i n a v e r s i o n i s prevented by b i l a t e r a l c o r t i c a l s preading d e p r e s s i o n induced s h o r t l y before CS p r e s e n t a t i o n . The f a c t t h a t g u s t a t o r y a f f e r e n t s reach the c o r t e x (Norgen & Leonard, 1971, 1973; Benjamin 6 Akert, 1959) and are important i n t a s t e a v e r s i o n l e a r n i n g a l s o argues f o r a hypothesis t h a t the g u s t a t o r y system i s capable of e n t e r i n g i n t o complex l e a r n i n g i n ways s i m i l a r to other sensory m o d a l i t i e s . 9 Current Status of Taste_ Aversion L e a r n i n g The above review suggests t h a t t a s t e - i l l n e s s l e a r n i n g may not d i f f e r too a p p r e c i a b l y from other types o f cue-consequence l e a r n i n g . L e a r n i n g , d e s p i t e long d e l a y s , no l o n g e r appears to be the e x c l u s i v e p r o v i n c e o f t a s t e a v e r s i o n l e a r n i n g (see Roberts, 1976, 1977, and L e t t , 1977 f o r d i s c u s s i o n of p o s s i b l e problems with at l e a s t one of L e t t ' s l o n g - d e l a y experiments). The n o t i o n of s p e c i f i c i t y i n cue-consequence a s s o c i a b i l i t y l e a r n i n g has c e r t a i n l y not gone unchallenged (Best e t a l . , 1973; Krane & Sagner, 1975; Bitterman, 1975). F u r t h e r , a unique n e u r a l s u b s t r a t a of t a s t e a v e r s i o n l e a r n i n g has y e t to be u n e q u i v o c a l l y demonstrated. 4 Stratec___ f o r Dealing, with P o s s i b l e Unique Aspects of Taste Aversion Learning In s p e c i f y i n g the uniqueness of a l e a r n i n g phenomenon i t i s important t o determine the major poin t s of s i m i l a r i t y and d i f f e r e n c e between one's phenomenon and other more t r a d i t i o n a l phenomena. One should then thoroughly i n v e s t i g a t e the apparent d i f f e r e n c e s , paying s p e c i a l a t t e n t i o n t o a r i g o r o u s f u n c t i o n a l a n a l y s i s , t o be sure of t h e i r e x i s t e n c e (Bitterman, 1976). T h i s s t r a t e g y was adopted i n the present r e s e a r c h . C e r t a i n compound s t i m u l u s c o n t r o l phenomena found with t r a d i t i o n a l l e a r n i n g procedures were examined i n the t a s t e a v e r s i o n l e a r n i n g procedure. The demonstration of s i m i l a r r e s u l t s between t a s t e - i l l n e s s l e a r n i n g and other cue-conseguences l e a r n i n g procedures was co n s i d e r e d an important adjunct t o the present concern over "uniqueness". Not only would the g e n e r a l i t y o f c e r t a i n l e a r n i n g 10 phenomena be i n c r e a s e d , but new p o s s i b i l i t i e s f o r manipulation and i n v e s t i g a t i o n would occur through the demonstration of s i m i l a r i t i e s . The demonstration o f these s i m i l a r i t i e s would a l s o serve to b e t t e r d e f i n e the boundaries of the "unigueness" o f t a s t e - i l l n e s s l e a r n i n g . Com£Ound Stimulus C o n t r o l r One very important aspect of the study o f any l e a r n i n g phenomenon concerns the a n a l y s i s of the c o n t r o l l i n g s t i m u l u s -response r e l a t i o n s governing a p a r t i c u l a r c o n d i t i o n e d behavior (Hay, 1969, 1972; Skinner, 1953; T e r r a c e , 1966; Ray & Sidman, 1970; Nevin, 1973). A c o n t r o l l i n g r e l a t i o n between a s t i m u l u s and response e x i s t s i f responding changes when a stimulus i s presented, or when an a s p e c t of a s t i m u l u s i s changed. Razran (1965) suggested that the study of c o n t r o l l i n g s timulus-response r e l a t i o n s present i n compound c o n d i t i o n i n g procedures i n which s e v e r a l CSs are p a i r e d with the UCS, while e x t e n s i v e l y i n v e s t i g a t e d by Russian experimenters, has been n e g l e c t e d by t h e i r Western c o u n t e r p a r t s . However, r e c e n t l y there has been c o n s i d e r a b l e r e s e a r c h concerned with compound stimulus c o n t r o l i n some sensory m o d a l i t i e s (Baker, 1968; Weiss, 1972). The l i t e r a t u r e concerning compound s t i m u l u s c o n t r o l i n the v i s u a l system i s e s p e c i a l l y e x t e n s i v e . Recent work with the pigeon i s an e x c e l l e n t example (e.g.., B u t t e r 1963; Johnson & Cumming, 1968; Johnson, 1970; Chase & Heineman, 1972; Blough, 1972; Zuckerman, 1973). Learning r e s e a r c h u s i n g the g u s t a t o r y system has always 11 been overshadowed by use of v i s u a l and a u d i t o r y s t i m u l i - There appears to be l i t t l e work on r a t s ' c o n d i t i o n e d behavior to g u s t a t o r y compounds and t h e i r r e s p e c t i v e component elements. There have been a few experiments i n v o l v i n g g u s t a t o r y - v i s u a l and a u d i t o r y compounds (experiments such as those of G a r c i a S K o e l l i n g , 1966, d e s c r i b e d e a r l i e r ) -There have a l s o been experiments on g u s t a t o r y - o l f a c t o r y compounds. T a u k u l i s & Revusky (1975), f o r example, gave r a t s c o n d i t i o n i n g t r i a l s where s a c c h a r i n alone was always f o l l o w e d by induced i l l n e s s , but the t a s t e of s a c c h a r i n p l u s the odor of amyl ac e t a t e was not- The r a t s l e a r n e d to d r i n k the s a c c h a r i n i n the presence of the odor, but to a v o i d i t when the odor was not present- T h i s , of course, i s a c o n d i t i o n a l d i s c r i m i n a t i o n , s a c c h a r i n consumption being c o n d i t i o n a l on the presence or absence of the odor- The r a t s were then presented with d i l u t e h y d r o c h l o r i c a c i d (HCl) which was f o l l o w e d by L i C l . One group was then t e s t e d f o r suppression of consumption of HCl i n the presence, of the odor of amyl a c e t a t e . T h i s group consumed more HCl than a group given o n l y HCl f o l l o w i n g H C l - L i C l p o i s o n i n g . T a u k u l i s and Revusky concluded t h a t the odor of amyl a c e t a t e had a c q u i r e d i n h i b i t o r y p r o p e r t i e s with r e s p e c t to avoidance behavior, i . e . , the odor i n h i b i t e d avoidance of the HCl. The e f f e c t s of the odor i n compound with the t a s t e s t i m u l u s was found to be p r e d i c t a b l e from Re s c o r l a 6 Wagner's (1972) model of c o n d i t i o n i n g . T h i s model was based on work with s t i m u l i and responses of a more t r a d i t i o n a l nature. T a u k u l i s & Revusky (1975) suggested that the g u s t a t o r y system i s l i k e other s t i m u l u s m o d a l i t i e s i n i t s c a p a c i t y to enter i n t o complex 12 c o n d i t i o n i n g r e l a t i o n s h i p s . There have been some experiments with s e g u e n t i a l l y presented f l a v o r s u s ing a t a s t e a v e r s i o n procedure (Revusky, 1971; Der-Karabetian S Gorry,1974; K a l a t & Rozin, 1970, 1971; Lindsey & Best, 1973). However, these were g e n e r a l l y not concerned with the sti m u l u s - r e s p o n s e r e l a t i o n s governing avoidance of the s e v e r a l elements, but r a t h e r were i n t e r e s t e d i n the problem of i n t e r f e r e n c e o c c u r r i n g between the CS and UCS. T h e r e f o r e , they used e x t r a s o l u t i o n s as i n t e r f e r i n g s t i m u l i imposed between the CS and UCS, and not as elements of a t a s t e compound. An example of t h i s r e s e a r c h i s Ka l a t and-. Rozin (1971). They found a v e r s i o n s to a sucrose s o l u t i o n even when f o l l o w e d by NaCl, c o f f e e and c a s e i n h y d r o l y s a t e , and then p o i s o n i n g . Der-Karabetian & Gorry (1974) have done a s i m i l a r experiment and r e p l i c a t e d K a l a t and Rozin's r e s u l t s . One could view both experiments as using compound s t i m u l i , where the elements occur s u c c e s s i v e l y r a t h e r than s i m u l t a n e o u s l y . These experiments could be taken as evidence f o r element c o n t r o l by sucrose when s e g u e n t i a l l y compounded with t h r e e other t a s t e elements. I t i s i n t e r e s t i n g t o note, however, t h a t Der-Karabetian S Gorry (1974) while o b t a i n i n g an a v e r s i o n to c o f f e e when i t was the t a s t e element c l o s e s t to the UCS d i d not o b t a i n an a v e r s i o n when i t was the f i r s t t a s t e element f o l l o w e d by three o t h e r s . One could view t h i s as overshadowing of c o f f e e by the other t h r e e s o l u t i o n s , provided one could show c o n t r o l by the oth e r s o l u t i o n s . These data were not- r e p o r t e d i n e i t h e r o f the above s t u d i e s . 13 There have been only a few papers d i r e c t l y concerned with compound g u s t a t o r y s t i m u l u s c o n t r o l (Malone 5 Cox, 1971; Lindsey & B e s t , 1973; Rzoska, 1953). Malone & Cox (1971) r e p o r t e d a study using a compound t a s t e s t i m u l u s of 0.25% s a c c h a r i n and 3% glucose- They r e p o r t e d c o n s i d e r a b l e avoidance of the s a c c h a r i n p l u s glucose compound and the s a c c h a r i n t a s t e element, but much l e s s avoidance of the glucose component. However, because of the obvious s i m i l a r i t y along the sweetness dimension of s a c c h a r i n and glucose t h i s study i s d i f f i c u l t t o i n t e r p r e t - Rzoska (1953) found some evidence of compound s t i m u l u s c o n t r o l of t a s t e a v e r s i o n s - He presented r a t s with v a r i o u s food bases l a c e d with poison. When the s u r v i v o r s were t e s t e d , i t was found t h a t they avoided the poi s o n t a s t e and 'the food base presented s e p a r a t e l y . The r a t s d i d not a v o i d new poisons or new bases u n l e s s the o f f e n d i n g poison t a s t e or food base was pr e s e n t . T h i s i s a f a i r l y c l e a r demonstration of c o n t r o l by both elements of a compound stimulus i n the g u s t a t o r y system of the r a t . pur£ose of the Present Research Because of the l a c k of any s y s t e m a t i c r e s e a r c h on the stimulus-response r e l a t i o n s governing avoidance of compound t a s t e s t i m u l i , the present r e s e a r c h on t a s t e a v e r s i o n l e a r n i n g with compound s t i m u l i was undertaken. I t was hoped t h a t by i n v e s t i g a t i n g c e r t a i n b a s i c c o n d i t i o n i n g phenomena a b e t t e r understanding of learned t a s t e a v e r s i o n s c o u l d be o b t a i n e d . The present s e r i e s of experiments was designed t o : f i r s t , e v a l u a t e Q the u s e f u l n e s s of combining t a s t e s o l u t i o n s i n a mixture to form a compound gus t a t o r y s t i m u l u s ; second, e l u c i d a t e some 14 t r a d i t i o n a l c o n d i t i o n i n g phenomena using the m i x e d - s o l u t i o n compound st i m u l u s approach; and t h i r d , a i d i n the d e l i n e a t i o n of the g u s t a t o r y - m a l a i s e system as a c o n d i t i o n a b l e cue-consequence system s i m i l a r to other more commonly s t u d i e d cue-consequence systems. The b a s i c method of the present r e s e a r c h , that of mixing t a s t e elements t o form compounds, was based on the assumption t h a t the t a s t e elements are r e a d i l y d e t e c t a b l e by the r a t as separate elements, and do not merge to form a q u a l i t a t i v e l y d i f f e r e n t s t i m u l u s . T'he experiments to be r e p o r t e d d e a l with s i x b a s i c c o n d i t i o n i n g phenomena. Experiments IA and IB i n v e s t i g a t e d c o n d i t i o n i n g t o t a s t e compounds and the subsequent c o n t r o l e x h i b i t e d by the r e s p e c t i v e t a s t e elements. Experiment II d e a l t with c o n t r o l by compound t a s t e s t i m u l i whose elements had been x n d i v i d u a l l y p a i r e d with the UCS. Experiment I I I i n v e s t i g a t e d the c o n d i t i o n i n g t o the elements of a t a s t e compound whose member elements were e i t h e r f a m i l a r (preexposed) or novel (not preexposed)- Experiment IV was concerned with the amount of avoidance behavior of a experiments V and VI were attempts t o demonstrate overshadowing (Pavlov, 1927), and the s i m i l a r phenomenon of b l o c k i n g (Kamin, 1968, 1969) r e s p e c t i v e l y . 15 2J_2l!J__:_:_i_;i2S 2J_ Experiments Each of the s i x major experiments to be d e s c r i b e d was composed of s e v e r a l sub-experiments. Because of the g e n e r a l s i m i l a r i t y of these sub-experiments to each o t h e r , they are a l l t r e a t e d as a u n i t i n terms of t h e i r methodology, r e s u l t s , and d i s c u s s i o n . Each sub-experiment i s designated by r e f e r r i n g to d i f f e r e n t groups (or c o n d i t i o n s ) and t h e i r r e s p e c t i v e treatments. Subj e c t s Male and female f i r s t , second, and t h i r d g e n e r a t i o n A g o u t i -Long-Evans hooded crossbreeds served as s u b j e c t s i n a l l experiments. Males and females were used i n order to i n c r e a s e the g e n e r a l i t y of the r e s u l t s . Eats were bred i n the U n i v e r s i t y of B r i t i s h Columbia's Biopsychology animal c o l o n y . Four Long-Evans hooded female r a t s were a l s o used i n one experiment. A l l r a t s were housed and t e s t e d i n standard i n d i v i d u a l home cages throughout a l l experiments- Access to standard Purina p e l l e t r a t chow was ad l i b . Hater or a s p e c i f i c c o n c e n t r a t i o n of S a c c h a r i n , NaCl, Sucrose, Quinine, Vinegar, C o f f e e , or compounds of these was a v a i l a b l e f o r 10 min per day depending on the procedure i n e f f e c t . Procedure General e x p e r i m e n t al p r o t o c o l c o n s i s t e d of a b a s e l i n e p e r i o d of s e v e r a l days during which time water deprived r a t s had 16 10 min access to water presented i n i n v e r t e d 50ml graduated c y l i n d e r s a t t a c h e d to t h e i r home cages. Follo w i n g s t a b l e b a s e l i n e water i n t a k e , e i t h e r c o n d i t i o n i n g or preexposure to s p e c i f i c s o l u t i o n s was begun. I f preexposure was i n e f f e c t each r a t r e c e i v e d 10 min access to the s o l u t i o n s on a given day or days. In some experiments tap water was presented f o r 10 min immediately f o l l o w i n g each s o l u t i o n . I f c o n d i t i o n i n g was i n e f f e c t a s o l u t i o n was presented f o r 10 min and f o l l o w e d w i t h i n 10 min by a 2% of body weight i n t r a p e r i t o n e a l i n j e c t i o n of 0.15 molar L i C l d i s s o l v e d i n tap water. On the day f o l l o w i n g the c o n d i t i o n i n g procedure, which may have been one or s e v e r a l s o l u t i o n - L i C l p a i r i n g s over days, the r a t s were given 10 min access to tap water. The t e s t i n g c y c l e s began on the f o l l o w i n g day. S o l u t i o n s were presented on s u c c e s s i v e days {usually completely counterbalanced a c r o s s a l l r a t s i n a group) f o r 10 min f o l l o w e d immediately by 10 min a c c e s s to tap water. T e s t i n g was continued u n t i l s e v e r a l consumption measures f o r each s o l u t i o n were obt a i n e d . Although a simultaneous two b o t t l e p r e f erence t e s t has been shown to be a more s e n s i t i v e measure of a v e r s i o n s (Grote & Brown, 1970; Dragoin, HcCleary, S McCleary, 1971), the s i n g l e b o t t l e t e s t was used i n the present s e r i e s because the a v e r s i o n s were g e n e r a l l y g u i t e l a r g e . A l l s o l u t i o n s were mixed by a weight t o volume procedure, except Vinegar which was volume t o volume. A l l of the s o l u t i o n s 17 and the s p e c i f i c c o n c e n t r a t i o n s used i n the present s e r i e s of experiments have been used e x t e n s i v e l y i n t a s t e a v e r s i o n r e s e a r c h , except perhaps Quinine which has been used t o a l e s s e r degree. Chemically most of the s o l u t i o n s d e a l t with i n the f o l l o w i n g experiments are c o n s i d e r e d to be i n e r t i n s o l u t i o n with water and with each other. By i n e r t i t i s meant t h a t they remain separate molecular substances and do not combine or change to form new molecules. Sucrose i n s o l u t i o n with a strong Vinegar s o l u t i o n w i l l r e a c t a f t e r s e v e r a l months by breaking down i n t o the i n e r t sugars of f r u c t o s e and glucose. A l s o the C o f f e e and Vinegar compound used i n Experiment I w i l l c h e m i c a l l y r e a c t over a p e r i o d of time. However, t h i s was minimized by mixing f r e s h s o l u t i o n s each day-18 EXPEEIMEWT IA £0S20JHD CONDITIONING WITH PEEEXPOSURE: CONTROL BT~ELEMENTS • Experiment IA was designed t o demonstrate c o n t r o l by the elements of a compound c o n d i t i o n e d s t i m u l u s f o l l o w i n g c o n d i t i o n i n g to the compound only-A l t hough overshadowing sometimes occurs i n other cue-conseguence systems, c o n t r o l by both elements of a compound i s g e n e r a l l y found (e.g.. B u t t e r , 1963). I f a compound t a s t e s o l u t i o n c o n s i s t i n g of a mixture of two d i s t i n c t i v e t a s t e s i s f o l l o w e d by t o x i c o s i s , an a v e r s i o n should occur not onl y to the compound, but to the i n d i v i d u a l t a s t e elements as w e l l , i f t a s t e a v e r s i o n l e a r n i n g i s not u n l i k e t r a d i t i o n a l cue-conseguence l e a r n i n g . The design of such an experiment r e q u i r e s that r a t s be t e s t e d with the i n d i v i d u a l f l a v o r s a f t e r compound-illness p a i r i n g . Since r a t s are neophobic (e-£, M i t c h e l l , e t a l . , 1975), they might d r i n k l e s s of these elements, not because they were pa r t of the compound, but because of the elements* no v e l t y - In order to r u l e out the p o s s i b l e c o n t r i b u t i o n o f neophobia, a l l f l a v o r s , i n c l u d i n g one s p e c i f i c a l l y not p a i r e d with t o x i c o s i s , were preexposed ( i . e . , simply presented alone) f o r a few s e s s i o n s . T h i s procedure i s e q u i v a l e n t to the le a r n e d s a f e t y procedure of Ka i a t & E o z i n (197 3) i n which f l a v o r s were presented to r a t s f o r s e v e r a l days p r i o r to CS-UCS p a i r i n g s . S e v e r a l groups of animals with -varying c o n d i t i o n i n g h i s t o r i e s were used i n order to i n c r e a s e g e n e r a l i t y -19 NaCl and S a c c h a r i n were used as components of one of the t a s t e compounds because of t h e i r e x t e n s i v e use i n the t a s t e a v e r s i o n l i t e r a t u r e . Sucrose and Quinine were chosen because of the w e l l known d i f f e r e n t i a l s e n s i t i v i t y of. the a n t e r i o r p o r t i o n of the tongue to sweet, and the p o s t e r i o r p o r t i o n t o b i t t e r (Kimura & B e i d l e r , 1961) . METHOD Subjects Each of four groups was composed of t h r e e male and three female r a t s (second and t h i r d g e n e r a t i o n Long-Evans-Agouti c r o s s b r e e d s ) . Group 1 r a t s were naive- Group 2 r a t s had been i n v o l v e d i n a p r i o r t a s t e a v e r s i o n experiment i n which they r e c e i v e d one 0.25% S a c c h a r i n - L i C l p a i r i n g a f t e r preexposure to NaCl, but not S a c c h a r i n . Group 3 c o n s i s t e d of r a t s t h a t had p r e v i o u s l y been exposed to one Compound (Saccharin and NaCl)-L i C l p a i r i n g and subseguently exposed to the Compound and i t s elements alone ( i . e . , e x t i n c t i o n ) . Group 4 had p r e v i o u s l y been exposed to one Compound (Sucrose and Q u i n i n e ) - L i C l p a i r i n g and then e x t i n c t i o n . Procedure Table 1 shows the s o l u t i o n s presented to each group during each major experimental phase. B a s e l i n e Preexposure Phase. A l l r a t s were exposed to the l i m i t e d f l u i d access regime f o r s e v e r a l days. Water i n t a k e was then recorded u n t i l consumption was s t a b l e - F o l l o w i n g t h i s , each 20 animal of Group 1 was given 10 min access t o each o f f o u r s o l u t i o n s (0.25% S a c c h a r i n , 1-0% NaCl, Saccharin+NaCl Compound, and 3-0% V i n e g a r ) , one each day, counterbalanced a c r o s s f o u r day TABLE 1 Summary of procedure f o r each group, showing t a s t e s o l u t i o n s presented i n each of the three major phases o f Experiment IA. Experimental phase C o n d i t i o n i n g B a s e l i n e ( S o l u t i o n - L i C l Test t r i a l s Group Preexposure p a i r i n g ) ( E x t i n c t i o n ) Saccharin NaCl Saccharin + NaCl Vinegar Saccharin NaCl Saccharin + NaCl Saccharin + NaCl Sac c h a r i n + NaCl Sac c h a r i n NaCl Saccharin + NaCl Vinegar Saccharin NaCl Saccharin + • NaCl 3S4 Quinine Sucrose Quinine + Sucrose Q u i n i n e + Sucrose Quinine Sucrose Quinine + Sucrose p r e s e n t a t i o n c y c l e s - T h i s f o u r day b a s e l i n e preexposure c y c l e o c c u r r e d twice. On the day f o l l o w i n g the second c y c l e water was presented f o r 10 min to a l l r a t s -C o n d ^ t i o n i n a Phase. The c o n d i t i o n i n g phase began on the next day. A l l s u b j e c t s were given 10 min access to the Compound of Sa c c h a r i n and NaCl f o l l o w e d by a standard L i C l i n j e c t i o n - The 21 same procedure was repeated on the f o l l o w i n g day- Water was presented the next day f o r 10 min. I g s t Phase. T e s t i n g i n e x t i n c t i o n began the f o l l o w i n g day. During t e s t i n g , a l l f o u r s o l u t i o n s were presented a c r o s s f o u r day c y c l e s , f o r 10 min each day. Each s o l u t i o n was f o l l o w e d by 10 min access to water- S o l u t i o n p r e s e n t a t i o n s during each four day c y c l e were counterbalanced across a l l animals. Each s u b j e c t r e c e i v e d f i v e t e s t p r e s e n t a t i o n s of each s o l u t i o n . Group 2 r a t s r e c e i v e d e s s e n t i a l l y the same treatment as Group 1, except t h e r e was no f o u r t h f l a v o r (e.g., V i n e g a r ) . Thus, the preexposure and t e s t i n g c y c l e s c o n s i s t e d of S a c c h a r i n , NaCl, and t h e i r Compound presented i n a counterbalanced order over t h r e e day t e s t sequences. Group 3 and 4 s u b j e c t s r e c e i v e d e s s e n t i a l l y the same treatment as Group 1 except f o r the t a s t e s o l u t i o n s (0.67mg Quinine/100 ml tap water, 3.0% Sucrose s o l u t i o n , a compound of Quinine and Sucrose, and a 1.0% NaCl s o l u t i o n ) , and number of Compound-LiCl p a i r i n g s . Group 3 r e c e i v e d f i v e Compound-LiCl p a i r i n g s , while Group 4 r e c e i v e d f o u r p a i r i n g s , a l s o , the non-paired t a s t e s o l u t i o n (NaCl) was presented only t h r e e times i n the e x t i n c t i o n t e s t s . Data P r e s e n t a t i o n and A n a l y s i s A c t u a l i n t a k e ( i n ml) of the v a r i o u s f l u i d s f o r the d i f f e r e n t groups during the b a s e l i n e , preexposure, c o n d i t i o n i n g , and e x t i n c t i o n phases of the experiment are shown g r a p h i c a l l y . Whether or not i n t a k e of a s o l u t i o n decreased between b a s e l i n e preexposure and the f i r s t e x t i n c t i o n t e s t t r i a l a f t e r c o n d i t i o n i n g was assessed by a repeated measures t - t e s t of 22 s i g n i f i c a n c e with n-1 degrees of freedom. Because i n t a k e of the v a r i o u s s o l u t i o n s sometimes d i f f e r e d d u r i n g b a s e l i n e , and because such d i f f e r e n c e s might be expected to p e r s i s t i n l a t e r p a r t s of the the experiment, comparisons between i n t a k e s of d i f f e r e n t s o l u t i o n s (e.g., on f i r s t e x t i n c t i o n t e s t t r i a l ) were done on sercentage change from b a s e l i n e preexposure s c o r e s . Since these comparisons were not always o r t h o g o n a l , s t a t i s t i c a l s i g n i f i c a n c e o f d i f f e r e n c e s i n percentage change i n i n t a k e was assessed by Tukey's HSD t e s t ( K i r k , 1968) with (k-1) (n-1) degrees of freedom and the a p p r o p r i a t e mean sguare r e s i d u a l e r r o r term. S i g n i f i c a n c e l e v e l s of 0.05 were used. A l l group comparisons are s i g n i f i c a n t u n l e s s otherwise noted. Because of the l a r g e number of comparisons and s i g n i f i c a n c e t e s t s performed, only the more important are presented i n the t e x t f o r the sake of c o n c i s e n e s s (a l i s t of comparisons and t e s t of s i g n i f i c a n c e r e s u l t s i s presented i n appendix A). RESULTS Fig u r e s 1-A, 1-B, 1-C, and 1-D shows f l u i d i n t a k e f o r a l l t a s t e s o l u t i o n s f o r Groups 1-4 r e s p e c t i v e l y . A l l f o u r f i g u r e s show e s s e n t i a l l y the same p a t t e r n of r e s u l t s . Consumption o f the compound and of the r e s p e c t i v e elements was reduced compared to p r e c o n d i t i o n i n g l e v e l s . However, the i n t a k e of the s o l u t i o n not p a i r e d with L i C l d i d not decrease from p r e c o n d i t i o n i n g l e v e l s . F i g u r e 1-A shows the r e s u l t s of Group 1. Intake of a l l 23 t a s t e s o l u t i o n s d u r i n g the second b a s e l i n e preexposure c y c l e (8) was high and comparable to that of water. F o l l o w i n g the f i r s t Compound-LiCl p a i r i n g (C), consumption of the Compound dropped d r a m a t i c a l l y . A marked r e d u c t i o n i n i n t a k e of NaCl, S a c c h a r i n , and t h e i r Compound occurred during the f i r s t e x t i n c t i o n p r e s e n t a t i o n (1) o f each s o l u t i o n . Compound i n t a k e was reduced from a mean preexposure l e v e l of 17 ml to a mean of 1.82 ml (t = 8.59). F i v e o f s i x animals showed l e s s than 0.5 ml consumption of the Compound during the f i r s t e x t i n c t i o n t e s t t r i a l . Every animal showed a reduced S a c c h a r i n i n t a k e , ranging from 20% to 80% of preexposure l e v e l s (t = 4.58). NaCl consumption was s i m i l a r l y reduced from b a s e l i n e preexposure l e v e l s (t = 8.89), with f i v e o f s i x animals showing r e d u c t i o n s of 85% or g r e a t e r . Intake of Vinegar, however, was u n a f f e c t e d . During the f i r s t t e s t t r i a l (1) Compound i n t a k e was l e s s than Saccharin i n t a k e (q = 8.8). A l l s i x animals showed g r e a t e r S a c c h a r i n i n t a k e than Compound i n t a k e . NaCl i n t a k e , however, was not d i f f e r e n t from Compound i n t a k e . Saccharin i n t a k e was g r e a t e r than NaCl i n t a k e (g = 7.68), with every animal showing g r e a t e r S a c c h a r i n than NaCl consumption. The animals drank c o n s i d e r a b l y l e s s of the Compound, S a c c h a r i n , and NaCl than Vinegar (g = 23.73, 15.19, 22.65; r e s p e c t i v e l y ) . During the second to f i f t h e x t i n c t i o n t r i a l a p r o g r e s s i v e l y g r e a t e r i n t a k e of the Compound and i t s elements o c c u r r e d . Intake of Vinegar remained a t high l e v e l s . Comparisons of s o l u t i o n i n t a k e s d u r i n g the second to f i f t h e x t i n c t i o n t r i a l s f o r each 2U 18 Q UJ _> 310 CO z o o 14- ^  TRIALS F i g u r e 1-A. B a s e l i n e preexposure, c o n d i t i o n i n g , and e x t i n c t i o n f l u i d i n t a k e f o r Group 1. The l a s t b a s e l i n e (B), a l l c o n d i t i o n i n g (C) , and a l l e x t i n c t i o n t r i a l s (1-5) are shown. F i l l e d symbols r e p r e s e n t i n t a k e of water {ffr ) , NaCl (___), S a c c h a r i n (___), Compound ( £ ) , and Vinegar ( ^ ) . U n f i l l e d symbols r e p r e s e n t water i n t a k e on the day of the f i r s t e x t i n c t i o n p r e s e n t a t i o n of each s o l u t i o n . Also shown are standard e r r o r s of the mean ( v e r t i c a l b a r s ) . s o l u t i o n g e n e r a l l y confirmed the r e s u l t s of the f i r s t t e s t seguence- Compound i n t a k e was lower than S a c c h a r i n i n t a k e i n a l l animals dur i n g the second and the t h i r d e x t i n c t i o n t e s t s . C o n t r a r y t o the f i r s t t e s t t r i a l , Compound i n t a k e was lower than 25 NaCl i n t a k e i n a l l animals during the second t e s t t r i a l (g = 6.6). Compound i n t a k e remained lower than NaCl through the f o u r t h t e s t . S a c c h a r i n i n t a k e was higher than NaCl i n t a k e d u r i n g the second t e s t t r i a l f o r a l l animals. Figure 1-B presents the r e s u l t s of Group 2. S u b s t a n t i a l l y the same r e s u l t s as those of Group 1 were ob t a i n e d . Reductions i n i n t a k e of a l l the s o l u t i o n s p a i r e d with t o x i c o s i s o c c u r r e d . Compound i n t a k e was reduced from a mean o f 14 ml to 0.17 ml (t = 11.47). A l l animals consumed l e s s than 0.5 ml of the Compound s o l u t i o n during the f i r s t t e s t t r i a l . NaCl i n t a k e was reduced from 14.75 ml to 5 ml {t = 5.51). Saccharin i n t a k e was reduced from a mean of 15.33 ml t o 2.92 ml (t = 9.95). Every animal showed reduced i n t a k e of NaCl and S a c c h a r i n , with many consuming l e s s than 20% of preexposure amounts. Compound i n t a k e during the f i r s t t e s t t r i a l was l e s s than NaCl i n t a k e (q = 4.86), but not S a c c h a r i n i n t a k e - Compound i n t a k e was lower than both NaCl and S a c c h a r i n i n t a k e f o r the remaining t e s t t r i a l s . There were no d i f f e r e n c e s between NaCl and S a c c h a r i n i n t a k e during the experiment. Intake of the Compound remained s u b s t a n t i a l l y lower than preexposure l e v e l s i n every animal f o r the d u r a t i o n of the experiment. Intake of NaCl r e t u r n e d to b a s e l i n e l e v e l s i n three animals by the second p r e s e n t a t i o n . Saccharin i n t a k e s t i l l was reduced i n every animal on i t s second p r e s e n t a t i o n -F i g u r e 1-C shows the r e s u l t s f o r Group 3. A l l preexposed t a s t e s o l u t i o n s were consumed at high l e v e l s . During the c o n d i t i o n i n g t r i a l s , i n t a k e of the Compound was reduced to low 26 B C C 1 , 2 3 4 5 TRIALS F i g u r e 1-B. B a s e l i n e preexposure, c o n d i t i o n i n g , and e x t i n c t i o n f l u i d i n t a k e f o r Group 2- See F i g u r e 1-A f o r e x p l a n a t i o n of symbols and l a b e l i n g . l e v e l s . Intake of Quinine, Sucrose and the Compound, but not NaCl was reduced on the f i r s t e x t i n c t i o n t e s t t r i a l . F i v e of s i x animals showed Compound consumption of l e s s than 0.5 ml (t = 10.35). Sucrose i n t a k e r e d u c t i o n s ranged from 38% to 99% (t = 5.98). Quinine i n t a k e r e d u c t i o n s ranged from 44% t o 99% (t = 7.57) . Compound i n t a k e during the f i r s t t e s t t r i a l d i d not d i f f e r 27 from Sucrose or Quinine i n t a k e . Intake of Sucrose and Quinine d i d not d i f f e r - Intake of the Compound, Sucrose, and Quinine was g r e a t l y reduced r e l a t i v e t o NaCl during the f i r s t t e s t t r i a l (g = 12.35, 9.94, 10.14; r e s p e c t i v e l y ) . Over the next four e x t i n c t i o n t r i a l s , i n t a k e of Quinine, Sucrose, and t h e i r Compound i n c r e a s e d . Compound i n t a k e remained reduced i n a l l animals r e l a t i v e t o i t s p r e e x p o s u r e - l e v e l s f o r the remaining f o u r e x t i n c t i o n t r i a l s . Consumption of Quinine remained reduced i n a l l animals f o r the next two t e s t t r i a l s . Sucrose i n t a k e remained reduced i n a l l animals f o r the second and t h i r d e x t i n c t i o n t r i a l s . NaCl i n t a k e was very high r e l a t i v e to i n t a k e of Compound, Sucrose, and Quinine i n a l l animals. Because of the slower recovery of Compound consumption r e l a t i v e to t h a t of Sucrose and Quinine, Compound i n t a k e during the second and t h i r d e x t i n c t i o n t r i a l s was lower than Quinine (second t e s t , q = 6.53), and lower than Sucrose on the t h i r d t e s t (q = 6-23). Compound i n t a k e was no lo n q e r s i g n i f i c a n t l y reduced r e l a t i v e t o Quinine i n t a k e by the f o u r t h t e s t t r i a l , but was s t i l l s i q n i f i c a n t l y lower than Sucrose. Intake of Sucrose and Quinine remained s i m i l a r throughout t e s t i n g . The r e s u l t s of Group 4 (Figure 1-D) are e s s e n t i a l l y i n aqreement with those of Group 3. A l l preexposed t a s t e s o l u t i o n s were consumed at high l e v e l s p r i o r to c o n d i t i o n i n g . During the f i r s t t e s t t r i a l f o l l o w i n g c o n d i t i o n i n g , i n t a k e of the Compound and t a s t e elements, Quinine and Sucrose, was reduced compared to preexposure l e v e l s (t = 15.64, 7.23, 16.96; r e s p e c t i v e l y ) . NaCl i n t a k e pre- and p o s t - c o n d i t i o n i n g d i d not d i f f e r . I I 1 I I I I I* I I I I BCCCCC 1 2 3 4 5 TRIALS F i g u r e 1-C. B a s e l i n e p r e e x p o s u r e , - c o n d i t i o n i n g , and e x t i n c t i o n f l u i d i n t a k e f o r Group 3. See Figure 1-A f o r e x p l a n a t i o n of a b s c i s s a l a b e l i n g . F i l l e d symbols r e p r e s e n t water ( ) , Sucrose ( H ) , Quinine ) , Compound ( ) , and NaCl {___,). U n f i l l e d symbols r e p r e s e n t corresponding water i n t a k e as e x p l a i n e d i n Figure 1-A. During the f i r s t t e s t t r i a l t h ere were no d i f f e r e n c e s between Compound and Sucrose, or Compound and Quinine i n t a k e . There was a l s o no d i f f e r e n c e between the i n t a k e s of Sucrose and Q u i n i n e . Intake of Compound, Quinine and Sucrose was c o n s i d e r a b l y reduced from NaCl i n t a k e (g = 14.5, 10.98, 13.58; 2 9 x BCCCC1 2 3 4 5 x - TRIALS F i g u r e 1-D. B a s e l i n e preexposure, c o n d i t i o n i n g , and e x t i n c t i o n f l u i d i n t a k e f o r Group 4. See F i g u r e 1-A f o r e x p l a n a t i o n of a b s c i s s a l a b e l i n g , and F i g u r e 1-C f o r e x p l a n a t i o n of the symbols. r e s p e c t i v e l y ) . During the remaining f o u r t e s t t r i a l s Compound i n t a k e remained reduced r e l a t i v e t o i t s preexposure l e v e l i n a l l animals- Sucrose i n t a k e a l s o remained reduced i n a l l animals f o r the d u r a t i o n of the experiment- Quinine i n t a k e remained reduced i n a l l animals on i t s second, but not subseguent t e s t 30 p r e s e n t a t i o n s . A comparison of s o l u t i o n i n t a k e s d u r i n g the second to f i f t h t e s t t r i a l s shows t h a t i n t a k e of Compound and Sucrose never d i f f e r e d . . Compound i n t a k e was c o n s i s t e n t l y lower than Quinine i n t a k e i n a l l animals d u r i n g the second and t h i r d t e s t s . Sucrose i n t a k e was lower than Quinine i n t a k e during the second and t h i r d t e s t c y c l e s . Two f u r t h e r p o i n t s should be made r e g a r d i n g the r e s u l t s of Experiment IA: f i r s t , an a n a l y s i s o f the raw data y i e l d e d e s s e n t i a l l y the same r e s u l t s as the a n a l y s i s of percent change ( t h i s i s t r u e of a l l experiments i n the present s e r i e s where percent t r a n s f o r m a t i o n data were an a l y z e d ) ; second, p o s t - t e s t water i n t a k e l e v e l s as shown i n F i g u r e 1-A were u n a f f e c t e d by i l l n e s s bouts. A lack of any p o s t - i l l n e s s e f f e c t on water i n t a k e was c h a r a c t e r i s t i c of the r e s u l t s o f every experiment i n the present s e r i e s . Summary of B e s u i t s Despite d i f f e r i n g h i s t o r i e s and v a r i a t i o n s i n procedures, r a t s preexposed to d i f f e r e n t f l a v o r s and then.to a p a i r i n g of a compound of two f l a v o r s and t o x i c o s i s drank l e s s of the compound and i t s component • f l a v o r s d u r i n g subsequent e x t i n c t i o n t r i a l s . Intake of a f l a v o r unpaired with t o x i c o s i s d i d not change. Since the r a t s were preexposed t o the compound elements, reduced i n t a k e of these f l a v o r s a f t e r compound-illness p a i r i n g cannot e a s i l y be a t t r i b u t e d to neophobia- Intake of the compound a f t e r c o n d i t i o n i n g was g e n e r a l l y l e s s than i n t a k e o f the elements. 31 Over a s e r i e s of e x t i n c t i o n t r i a l s the animals drank more of the compound and component f l a v o r s . A v e r s i o n t o the compound e x t i n g u i s h e d most s l o w l y . 32 J I E I 1 I M J J T 12 COMPOUND CONDITIONING J_ITHOUT PREEXPOS0Hi CONTROL BY ELEM ENTS Th i s experiment was a s y s t e m a t i c r e p l i c a t i o n of Experiment I I - The same b a s i c procedure as i s Experiment IA was used, but without preexposing the t o - b e - c o n d i t i o n e d t a s t e s t i m u l i - T h i s was done i n order to assess the c o n d i t i o n i n g of a v e r s i o n s t o novel compounds and t h e i r r e s p e c t i v e elements f o l l o w i n g compound-toxicosis p a i r i n g . S u b j e c t s were a l s o t e s t e d i n order to determine the e f f e c t s , i f any, o f a g e n e r a l neophobic r e a c t i o n to n o v e l t a s t e s t i m u l i f o l l o w i n g c o n d i t i o n i n g to other novel t a s t e s t i m u l i . METHOD Sub j e c t s Four groups of r a t s were used. Group 1 c o n s i s t e d of f o u r male crossbreeds and f o u r female Long-Evans hooded r a t s . Groups 2, 3, and 4 each c o n s i s t e d of t h r e e male and three female c r o s s b r e e d s . A l l s u b j e c t s were naive with r e s p e c t to t a s t e -t o x i c o s i s c o n d i t i o n i n g -Procedure Table 2 shows the s o l u t i o n s presented to each group i n each major phase of Experiment IB. A l l r a t s were exposed to the l i m i t e d f l u i d access regime f o r s e v e r a l days. Water i n t a k e was then recorded f o r s e v e r a l days. C o n d i t i o n i n g Phase, on the f o l l o w i n g day a l l r a t s were given 10 min access t o a novel t a s t e s o l u t i o n . Group 1 r a t s r e c e i v e d 33 access to a compound s o l u t i o n of 1-0% NaCl and 0-25% Sacch a r i n -Group 2 r e c e i v e d a compound s o l u t i o n of 0.67mg Quinine per 100ml of tap water, and 3-0% Sucrose. Groups 3 and 4 r e c e i v e d access TABLE 2 Summary of procedure f o r each group, showing t a s t e s o l u t i o n s presented i n each of the two major phases of Experiment IB.. Experimental phase C o n d i t i o n i n g Test t r i a l s Group ( S o l u t i o n - L i C l p a i r i n g ) ( E x t i n c t i o n ) NaCl+Saccharin NaCl+Saccharin NaCl S a c c h a r i n Quinine+Sucrose Quinine+Sucrose Quinine Sucrose Vinegar Vinegar NaCl+Saccharin Sa c c h a r i n NaCl Vinegar Vinegar Quinine+Sucrose Quinine Sucrose to a 3.0% Vinegar s o l u t i o n . F o l l o w i n g t h i s , a l l r a t s were i n j e c t e d with L i C l . On the next day a l l r a t s r e c e i v e d 10 min a c c e s s to water. Test Phase. On the f o l l o w i n g day t e s t i n g i n e x t i n c t i o n began. Each s u b j e c t of Groups 1 and 2 r e c e i v e d a d i f f e r e n t order of the t h r e e t a s t e s o l u t i o n s (Compound and i t s r e s p e c t i v e elements) over s u c c e s s i v e t h r e e day t e s t c y c l e s u n t i l s e v e r a l consumption 34 measures f o r each s o l u t i o n were obtained- Group 3 was t e s t e d i n e x t i n c t i o n with the o r i g i n a l Vinegar s o l u t i o n , a 0.25% Saccharin s o l u t i o n , a 1.0% NaCl s o l u t i o n , and a Compound of S a c c h a r i n and NaCl over 4 day t e s t c y c l e s . Group 4 r e c e i v e d t e s t p r e s e n t a t i o n s of Vinegar, a 3.0% Sucrose s o l u t i o n , a Quinine s o l u t i o n and a compound of Sucrose and Quinine counterbalanced over f o u r day c y c l e s . Each s o l u t i o n was a v a i l a b l e f o r 10 min on a given day f o l l o w e d by 10 min access to tap water. Data P r e s e n t a t i o n and A n a l y s i s This aspect of the experiment was s i m i l a r to t h a t of Experiment IA. S o l u t i o n i n t a k e s {in ml) d u r i n g t e s t i n g were compared with each other and with c o n d i t i o n i n g day in t a k e of the s o l u t i o n p a i r e d with i l l n e s s . A l l comparisons were made with Tukey's HSD t e s t . RESULTS F l u i d i n t a k e f o r Groups 1 and 2 r a t s shows c l e a r l y t h a t p a i r i n g a novel compound s o l u t i o n with t o x i c o s i s r e s u l t s i n a decrease i n consumption of the t a s t e elements as w e l l as of the compound. Groups 3 and 4 show t h a t p r i o r c o n d i t i o n i n g with Vinegar does not r e s u l t i n suppressed i n t a k e of NaCl, Sucrose, or Quinine. However, a Sac c h a r i n i n t a k e r e d u c t i o n r e l a t i v e to NaCl and a NaCl+Saccharin Compound d i d occur during the f i r s t t e s t c y c l e . F i g u r e 1-E, panel 1, shows the r e s u l t s of Group 1. The l a r g e s t r e d u c t i o n i n f l u i d i n t a k e , r e l a t i v e to intake of the TRIALS F i g u r e 1-E. C o n d i t i o n i n g and e x t i n c t i o n f l u i d i n t a k e f o r a l l groups of Experiment IB. Panels 1 and 2 show f l u i d i n t a k e f o r Groups 1 and 2 r e s p e c t i v e l y . Panel 1 ( f i l l e d symbols) shows water ( ) , NaCl ( A ) ' Saccharin ( 0 ) and Compound ( 0 ) i n t a k e ( u n f i l l e d symbols correspond to f i r s t e x t i n c t i o n t r i a l i n t a k e of corresponding f i l l e d symbols). Panel 2 ( f i l l e d symbols) shows water ( ( } ) # Quinine ( ) , Sucrose ( _ | ) # and Compound ( 0 ) i n t a k e ( u n f i l l e d symbols same as Panel 1 ) . Panels 3 and 4 show f l u i d i n t a k e f o r Groups 3 and 4 r e s p e c t i v e l y . F i l l e d symbols of panel 3 show the same s o l u t i o n s as panel 1 with the a d d i t i o n of Vinegar ( ^ ) . F i l l e d symbols of panel 4 show the same s o l u t i o n s as Panel 2 with the a d d i t i o n of Vinegar Compound on the c o n d i t i o n i n g day, occurred with the Saccharin+NaCl Compound. Compound i n t a k e decreased from a 36 c o n d i t i o n i n g day mean l e v e l of 12.2 ml to 0.26 ml (g = 11.25). A s m a l l e r r e d u c t i o n t o a mean of 5.7 ml occu r r e d i n Sac c h a r i n i n t a k e (g = 6.14). NaCl i n t a k e was reduced to a mean of 6 ml (g = 5.83). A l l e i g h t animals showed t h i s reduced i n t a k e , while seven showed r e d u c t i o n s to NaCl and Sac c h a r i n o f between 50% and 70% r e l a t i v e t o Compound i n t a k e during c o n d i t i o n i n g . Consumption of both elements during the f i r s t e x t i n c t i o n t e s t t r i a l was g r e a t e r than consumption of the Compound (NaCl, g = 5.41; S a c c h a r i n , g = 5.11). There was no d i f f e r e n c e i n consumption of NaCl and Sac c h a r i n d u r i n g c o n d i t i o n i n g . Compound i n t a k e ( r e l a t i v e to c o n d i t i o n i n g day l e v e l s ) remained reduced i n a l l animals on the second and t h i r d t e s t p r e s e n t a t i o n s . Neither S a c c h a r i n or NaCl i n t a k e was reduced ( r e l a t i v e to c o n d i t i o n i n g day i n t a k e of the Compound) d u r i n g the second t e s t . Compound i n t a k e remained lower than NaCl i n t a k e i n a l l animals during the second and t h i r d t e s t c y c l e s . Compound i n t a k e was c o n s i s t e n t l y lower than S a c c h a r i n i n t a k e i n a l l animals d u r i n g the f i r s t , second, and t h i r d t e s t c y c l e s . Intake o f these s o l u t i o n s over the next three e x t i n c t i o n t r i a l s shows a gradual r e c o v e r y to p r e c o n d i t i o n i n g l e v e l s . Panel 2 of F i g u r e 1-E shows pre- and p o s t - c o n d i t i o n i n g f l u i d i n t a k e f o r Group 2. Intake of the Compound was reduced g r e a t l y i n a l l animals f o l l o w i n g two Compound-LiCl p a i r i n g s , going from a mean of 14.16 ml t o 1.05 ml (q = 28.58). Sucrose and Quinine i n t a k e was reduced from c o n d i t i o n i n g day Compound i n t a k e l e v e l s (g = 28.34 and 21.0; r e s p e c t i v e l y ) . A l l animals showed Quinine consumption of between 3 and 6 ml. Sucrose i n t a k e 37 ranged from 0-1 t o 2-5 ml- Compound and Sucrose i n t a k e d i d not d i f f e r on the f i r s t e x t i n c t i o n t r i a l - Quinine i n t a k e was, however, c o n s i s t e n t l y higher i n a l l animals than the f i r s t e x t i n c t i o n t r i a l i n t a k e of Compound (g = 7.32) or Sucrose (g = 7.17). Compound i n t a k e ( r e l a t i v e t o c o n d i t i o n i n g day l e v e l s ) remained reduced d u r i n g the second t e s t t r i a l , but not the t h i r d . Sucrose i n t a k e was reduced a l s o i n a l l animals on the second, but not the t h i r d t e s t t r i a l - Quinine i n t a k e remained reduced i n a l l animals f o r the second and t h i r d t e s t t r i a l s . Compound and Sucrose i n t a k e never d i f f e r e d during e x t i n c t i o n . Compound i n t a k e was lower than Quinine on the second p r e s e n t a t i o n . Quinine and Sucrose were not d i f f e r e n t on the second t e s t . F i g u r e 1-E, panel 3, presents the r e s u l t s f o r Group 3. Intake of Vinegar (the c o n d i t i o n e d stimulus) was reduced from i n t a k e l e v e l s on the c o n d i t i o n i n g day (g = 6.68), and from the i n t a k e of the f i r s t t e s t t r i a l of NaCl (g = 13.75), S a c c h a r i n (g = 5.71), and the Compound (q = 9.31). NaCl i n t a k e was not reduced- S a c c h a r i n i n t a k e was not d i f f e r e n t from c o n d i t i o n i n g day i n t a k e of Vinegar. Consumption of Vinegar i n c r e a s e d over t e s t t r i a l s . F i g u r e 1-E, panel 4, shows the r e s u l t s f o r Group 4. One V i n e g a r - L i C l p a i r i n g d i d not r e s u l t i n any a p p r e c i a b l e r e d u c t i o n i n i n t a k e of the novel s o l u t i o n s of Sucrose, Quinine, or t h e i r Compound. Vinegar i n t a k e was reduced f o l l o w i n g one c o n d i t i o n i n g t r i a l (g = 11-34). Vinegar i n t a k e remained reduced i n a l l animals on the second t e s t p r e s e n t a t i o n . 38 Summary, of Resu l t s P a i r i n g of a compound of two novel f l a v o r s with i l l n e s s produces an a v e r s i o n t o the component f l a v o r s as w e l l as to the compound. A g e n e r a l neophobic r e a c t i o n cannot account f o r these r e s u l t s . DISCUSSION The r e s u l t s of Experiment IA c l e a r l y demonstrated c o n t r o l by the elements of a gus t a t o r y compound s t i m u l u s . Groups 1 and 2 demonstrated t h i s e f f e c t f o r a compound c o n s i s t i n g of the elements NaCl and S a c c h a r i n . Consumption of Vinegar unpaired with L i C l demonstrated t h a t the e f f e c t was not a g e n e r a l neophobic r e a c t i o n , but r a t h e r was c o n f i n e d t o those s t i m u l u s elements which were members of the c o n d i t i o n e d compound. In f a c t the degree of s u p p r e s s i o n to the elements was r a t h e r s t r i k i n g . S a c c h a r i n consumption of Group 1 was reduced approximately 60%. NaCl i n t a k e was reduced over 80%. Compound i n t a k e , of course, was reduced f u r t h e r , t o approximately 10% of i t s c o n d i t i o n i n g day l e v e l . Group 2 showed a s i m i l a r l y l a r g e r e d u c t i o n i n consumption t o the component t a s t e elements and the Compound. The r e s u l t s of Groups 3 and 4, which r e c e i v e d Quinine and Sucrose compound c o n d i t i o n i n g , showed t h a t element c o n t r o l a f t e r Compound c o n d i t i o n i n g was not l i m i t e d to NaCl and Sac c h a r i n compounds. C o n s i d e r i n g the d i f f e r i n g past h i s t o r i e s of Grou.ps 3 and 4 the s i m i l a r i t y of t h e i r behavior suggests a powerful and c o n s i s t e n t e f f e c t . The l a c k of any reduced i n t a k e of the unpaired NaCl s o l u t i o n again supports the s p e c i f i c i t y of the 39 e f f e c t . NaCl i n t a k e , as shown by Groups 1 and 2, was h i g h l y s u s c e p t i b l e t o c o n d i t i o n i n g and yet showed no s i g n s of su p p r e s s i o n even a f t e r as many as f i v e Sucrose-Quinine Compound-L i C l p a i r i n g s . The r e s u l t s of Experiment IB, Groups 1 and 2, extend the r e s u l t s of Experiment IA to no v e l f l a v o r compounds and t h e i r r e s p e c t i v e elements. I t i s a l s o c l e a r from the r e s u l t s of Groups 3 and 4 that f o l l o w i n g a novel t a s t e s o l u t i o n such as Vinegar with L i C l does not reduce subsequent i n t a k e o f a 1.0% NaCl, a 3.0% Sucrose, or a 0.67 mq Quinine/100 ml tap water s o l u t i o n . Although i n t a k e of S a c c h a r i n f o l l o w i n q V i n e q a r - L i C l p a i r i n g was reduced somewhat r e l a t i v e to water i n t a k e , i t does not appear t h a t t h i s reduced i n t a k e was due to the V i n e q a r - L i C l p a i r i n g . In f a c t i t was observed c o n s i s t e n t l y throughout the present s e r i e s o f experiments t h a t the f i r s t p r e s e n t a t i o n of the 0.25% Sa c c h a r i n s o l u t i o n was always somewhat reduced from t h a t of b a s e l i n e water i n t a k e . Because of t h i s r a t h e r l a r g e neophobic r e a c t i o n one would have to perform a between groups a n a l y s i s to determine e x a c t l y how much of the Sa c c h a r i n s u p p r e s s i o n f o l l o w i n g S a c c h a r i n + N a C l - L i C l p a i r i n g was due t o c o n d i t i o n i n g , and how much was due to any neophobic r e a c t i o n . T h i s has not been done mainly because i t seems q u i t e e v i d e n t from the r e s u l t s of Experiment IA t h a t r a t s are capable of respondinq t o S a c c h a r i n i n compound with NaCl. I f one c o n s i d e r s the ad a p t i v e s i q n i f i c a n c e of a g u s t a t o r y system t h a t i s able to respond to the elements of a compound of f l a v o r s as well as to the compound i t s e l f , i t becomes r e a d i l y 4 0 understandable why such an a b i l i t y should e x i s t . An animal, e s p e c i a l l y the v i s u a l l y l e s s endowed r a t , must depend a great d e a l on i t s t a s t e system f o r d i s t i n g u i s h i n g p o t e n t i a l sources of rood from sources of malaise. Thus, the r a t must be a b l e to i d e n t i f y a harmful element even i f i t i s l a t e r found t o be i n a d i f f e r e n t c ontext than t h a t o r i g i n a l l y t a s t e d and f o l l o w e d by s i c k n e s s . Experiments IA and IB a t t e s t to the a b i l i t y of the r a t s ' g u s t a t o r y system to separate the d i f f e r e n t t a s t e s present i n a compound and respond a c c o r d i n g l y . The r e s u l t s of Experiments IA and IB argue s t r o n g l y f o r viewing the g u s t a t o r y system of the r a t as capable of e n t e r i n g i n t o complex s t i m u l u s -response r e l a t i o n s t y p i c a l of c o n d i t i o n i n g i n other more t r a d i t i o n a l stimulus-conseguence procedures. One f e a t u r e of compound s t i m u l u s c o n t r o l which i s sometimes observed i n t r a d i t i o n a l i n s t r u m e n t a l l e a r n i n g procedures i s unequal c o n t r o l of responding by the separate elements of a compound s t i m u l u s (e.<_., Johnson & Cumming, 1 968). On the other hand, more-or-less equal c o n t r o l by the elements i s sometimes found (e.g_., Butter, 1963). Razran (1965) r e p o r t s a P a v l o v i a n study by Elyassan i n 1938 with dogs i n which an e f f e c t s i m i l a r t o the l a t t e r was o b t a i n e d . The s a l i v a r y r e f l e x was c o n d i t i o n e d t o a musical chord CS c o n s i s t i n g of three component notes, G, C, and F. Elayassan found f a i r l y equal c o n t r o l by each element, while the compound e l i c i t e d a g r e a t e r s a l i v a r y r e f l e x . Experiments IA and IB showed t h a t , over groups, t h e r e was g e n e r a l l y no c l e a r d i f f e r e n t i a l s u p p r e s s i o n t o one element of the Compound. Each i n d i v i d u a l s u b j e c t showed some d i f f e r e n t i a l c o n t r o l , but i t was not great i n any s u b j e c t . Group 1 i n 41 Experiment IA d i d show a r a t h e r strong "overshadowing" e f f e c t of S a c c h a r i n by NaCl. The p o s s i b l e reasons f o r t h i s w i l l be d e a l t with i n the d i s c u s s i o n of the r e s u l t s f o r Experiment V, the overshadowing experiment. 42 EXPEEIHENT I I COMPOONDING SEPAR ATELY~*CONDITIONED TASTE ELEMENTS T h i s experiment was designed t o determine i f two c o n d i t i o n e d a v e r s i v e t a s t e elements w i l l form a compound which w i l l a l s o be avoided- I f two t a s t e elements are s e p a r a t e l y f o l l o w e d by i l l n e s s , a subseguent combination o f these should r e s u l t i n an a v e r s i o n equal to (or g r e a t e r than) t h a t t o each element. A r e s u l t such as t h i s would be expected on the b a s i s of the response summation l i t e r a t u r e from t r a d i t i o n a l l e a r n i n g paradigms (Henderson, 1975; Weiss, 1964, 1972; Wolf, 1963; M i l l e r , 1969; van Houten, O'Leary, £ Weiss, 1970). Response summation occurs when the compound of two c o n d i t i o n e d s t i m u l i c o n t r o l s more responding than e i t h e r element presented s e p a r a t e l y (Weiss, 1972). In order to f a c i l i t a t e the p o s s i b i l i t y o f observing a summation e f f e c t , one group of r a t s was provided with a s a l i e n t s o l u t i o n not p a i r e d with t o x i c o s i s . I t has been suggested by Weiss (1972) t h a t a d i s t i n g u i s h a b l e s t i m u l u s not a s s o c i a t e d with an a v e r s i v e event i s necessary before a la r g e summation e f f e c t w i l l occur. METHOD s u b j e c t s Four groups of f i r s t , second, and t h i r d g e n e r a t i o n c r o s s b r e e d s served as s u b j e c t s . Each group c o n s i s t e d of three male and three female r a t s , except Group 2 which was composed of 43 two males and three females due to the death of one r a t -Procedure Table 3 shows the s o l u t i o n s presented to each group i n each major experimental phase. Group 1 r a t s r e c e i v e d one N a C l - L i c l TABLE 3 Summary of procedure f o r each group, showing t a s t e s o l u t i o n s presented i n each of the two major phases of Experiment I I . Experimental phase C o n d i t i o n i n g Test t r i a l s Group ( S o l u t i o n - L i C l p a i r i n g ) ( E x t i n c t i o n ) NaCl Saccharin+NaCl 1&2 S a c c h a r i n Saccharin NaCl NaCl Saccharin+NaCl 3 S a c c h a r i n S a c c h a r i n Vinegar NaCl (not paired) Vinegar C o f f e e * V i n e g a r 4 Coffee C o f f e e Vinegar Vinegar Saccharin+NaCl and one S a c c h a r i n - L i C l p a i r i n g i n a counterbalanced order. One day with water alone i n t e r v e n e d between s u c c e s s i v e p a i r i n g s . One water-only day was a l s o i n t e r s p e r s e d between c o n d i t i o n i n g and t e s t i n g . In the t e s t i n g c y c l e NaCl, S a c c h a r i n , and t h e i r compound were presented i n a counterbalanced order a c r o s s a l l animals over t h r e e day p e r i o d s . Each r a t r e c e i v e d p r e s e n t a t i o n of Compound, NaCl, and S a c c h a r i n s e v e r a l times. 44 Group 2 r a t s were t r e a t e d i n an i d e n t i c a l manner t o those of Group 1 except t h a t the compound of NaCl and S a c c h a r i n was always presented f i r s t to a l l r a t s i n each t h r e e day t e s t c y c l e -P r e s e n t a t i o n of NaCl and S a c c h a r i n was counterbalanced over the remaining two days of each t h r e e day t e s t c y c l e -Group 3 r a t s were t r e a t e d i d e n t i c a l l y to those of Group 1 except t h a t a 2.5% Vinegar s o l u t i o n was presented i n s t e a d of water on the day f o l l o w i n g each s o l u t i o n - t o x i c o s i s p a i r i n g . A l l r a t s i n i t i a l l y r e c e i v e d a s o l u t i o n - t o x i c o s i s p a i r i n g ( e i t h e r NaCl or S a c c h a r i n ) , then one day with 10 min access to the Vinegar s o l u t i o n . F o l l o w i n g t h i s , another s o l u t i o n - t o x i c o s i s p a i r i n g o c curred, f o l l o w e d the next day by 10 min access to the Vinegar s o l u t i o n . On the next day the t e s t i n g c y c l e as d e s c r i b e d f o r Group 1 s t a r t e d . The Vinegar s o l u t i o n was given once to a l l r a t s a f t e r the f i r s t three day t e s t c y c l e . Group 4 r a t s a l s o were t r e a t e d s i m i l a r l y t o those of Group 1 except f o r two d i f f e r e n c e s . Instead of NaCl and S a c c h a r i n s e r v i n g as the c o n d i t i o n e d t a s t e s t i m u l i , a 0.5% C o f f e e ( i n s t a n t Sanka) and a 2-5% Yinegar s o l u t i o n were used. Als o i n order t o t e s t f o r suppression to a novel compound f o l l o w i n g p r i o r c o n d i t i o n i n g to an u n r e l a t e d t a s t e element, the compound of NaCl and S a c c h a r i n used f o r Groups 1, 2, and 3 was presented during the f i r s t t e s t c y c l e . SlLiS. P r e s e n t a t i o n and A n a l y s i s The format and procedures were s i m i l a r t o Experiments IA and IB. A l l comparisons were made with Tukey's HSD t e s t . BES0LTS The r e s u l t s of a l l the groups c l e a r l y demonstrated t h a t , the compound was t r e a t e d as being composed of the two a v e r s i v e elements and not as a novel s o l u t i o n . Intake r e d u c t i o n s of the compound of the c o n d i t i o n e d elements was e i t h e r equal t o or g r e a t e r than the suppression to e i t h e r t a s t e element presented s e p a r a t e l y . Some evidence f o r summation was found. Evidence of the s p e c i f i c i t y o f c o n d i t i o n i n g was shown. Figure 2-A shows the r e s u l t s f o r Group 1. Consumption of the Compound was reduced r e l a t i v e t o consumption of both f l u i d s on c o n d i t i o n i n g t r i a l s ( S accharin, g = 10.3; NaCl, g = 21.0). Compound consumption ranged between 0.1 ml and 0.5 ml f o r f i v e of s i x animals , while one consumed 3-5 ml. Consumption of both element s o l u t i o n s was reduced compared to i n t a k e of these dur i n g c o n d i t i o n i n g t r i a l s . NaCl consumption ranged between 0.1 ml and 3 ml (g = 19.6), while S a c c h a r i n consumption ranged between 0-1 ml and 1.5 ml (q = 10.4). There was no d i f f e r e n c e d u r i n g the f i r s t t e s t t r i a l between consumption of NaCl or Saccharin r e l a t i v e to the Compound. The remaining t e s t t r i a l s show i n c r e a s i n g consumption f o r each t a s t e s o l u t i o n . Note e s p e c i a l l y the c r o s s over on the t h i r d p r e s e n t a t i o n of Saccharin and the Compound. F i v e of s i x animals showed t h i s e f f e c t . Compound i n t a k e was reduced on i t s second p r e s e n t a t i o n r e l a t i v e to NaCl i n t a k e during c o n d i t i o n i n g , but was recovered by the t h i r d t r i a l . Compound i n t a k e was not reduced r e l a t i v e to c o n d i t i o n i n g day i n t a k e o f S a c c h a r i n during the second or subseguent p r e s e n t a t i o n s . NaCl i n t a k e on the 46 - J L_ 1 I I I L B C 1 2 3 4 5 TRIALS F i g u r e 2-A. C o n d i t i o n i n g and e x t i n c t i o n f l u i d i n t a k e f o r Group 1- See F i g u r e 1-A f o r a b s c i s s a l a b e l i n g and e x p l a n a t i o n of f i l l e d and u n f i l l e d symbols-second p r e s e n t a t i o n was s t i l l reduced r e l a t i v e to c o n d i t i o n i n g day i n t a k e , while Saccharin i n t a k e was at c o n d i t i o n i n g day i n t a k e l e v e l s - The most i n t e r e s t i n g data of t h i s second p r e s e n t a t i o n of s o l u t i o n s was the i n t a k e of the Compound r e l a t i v e to the i n t a k e of both NaCl and Saccha r i n - Compound i n t a k e was c o n s i d e r a b l y reduced r e l a t i v e t o NaCl i n f o u r of s i x animals, the same i n one, and s l i g h t l y higher i n one (g = 4-53). S a c c h a r i n i n t a k e was higher than Compound i n t a k e i n f i v e of s i x 47 animals, and equal i n one (q = 4.72). These d i f f e r e n c e s suggest a summation e f f e c t . F i g u r e 2-B shows the r e s u l t s of Group 2. Consumption of the Compound was reduced r e l a t i v e t o consumption of both s o l u t i o n s on c o n d i t i o n i n g t r i a l s (NaCl, q = 13.41; S a c c h a r i n , q = 6.5). Compound consumption ranged between 0.5 ml and 1.5 ml. Consumption of NaCl and S a c c h a r i n a l s o d i f f e r e d from i n t a k e of these during c o n d i t i o n i n g t r i a l s (q = 9.33, 5.33; r e s p e c t i v e l y ) . There was no d i f f e r e n c e d u r i n g the f i r s t t e s t between i n t a k e of S a c c h a r i n or NaCl r e l a t i v e to the Compound ( i . e . , no summation e f f e c t ) , although f o u r of f i v e animals showed g r e a t e r s u p p r e s s i o n to the Compound than to e i t h e r element duri n g the f i r s t t e s t seguence, t h i s i s confounded with o r d e r of p r e s e n t a t i o n . The e x t i n c t i o n data agree well with that o f Group 1. Compound i n t a k e was reduced on the second t r i a l r e l a t i v e to NaCl i n t a k e during c o n d i t i o n i n g , but not r e l a t i v e t o S a c c h a r i n . NaCl i n t a k e on the second t r i a l was no l o n g e r d i f f e r e n t r e l a t i v e t o the i n t a k e of t h i s s o l u t i o n on the c o n d i t i o n i n g day. Contrary t o Group 1, only NaCl was consumed i n l a r g e r amounts than the Compound i n a l l animals. Also note the c r o s s o v e r of the e x t i n c t i o n curves of the Compound and Saccharin s o l u t i o n s on the t h i r d t e s t p r e s e n t a t i o n . Although t h i s e f f e c t was c l e a r l y observed i n f o u r out of f i v e r a t s , s i g n i f i c a n c e was not reached. The r e s u l t s f o r Group 3, which r e c e i v e d " s a f e " Vinegar to enhance any summation e f f e c t , are presented i n F i g u r e 2-C. The p r e d i c t i o n t h a t i n t a k e of the Compound of NaCl and S a c c h a r i n 48 I I I I I I ! ; B C 1 2 3 4 TRIALS F i g u r e 2-B. C o n d i t i o n i n g and e x t i n c t i o n f l u i d i n t a k e f o r Group 2. See F i g u r e 1-A f o r a b s c i s s a l a b e l i n g and e x p l a n a t i o n of f i l l e d and u n f i l l e d symbols-would be c o n s i s t e n t l y l e s s than the s u p p r e s s i o n to e i t h e r element was not upheld. Group 3*s r e s u l t s e s s e n t i a l l y r e p l i c a t e d those of Groups 1 and 2. During the c o n d i t i o n i n g days there was no decrease i n i n t a k e of the unpaired s o l u t i o n (Vinegar). However, f o l l o w i n g the c o n d i t i o n i n g phase, i n t a k e of a l l other t a s t e s o l u t i o n s decreased d r a m a t i c a l l y . During the f i r s t t e s t t r i a l t h e r e were no d i f f e r e n c e s 49 \ i i i i i i i B C 1 2 3 4 5 TRIALS F i g u r e 2-C. C o n d i t i o n i n g and e x t i n c t i o n f l u i d i n t a k e f o r Group 3. See F i g u r e 1-A f o r a b s c i s s a l a b e l i n g and e x p l a n a t i o n of f i l l e d and u n f i l l e d symbols except f o r the a d d i t i o n of Vinegar ( T i -bet ween s o l u t i o n i n t a k e s - However, during the second t e s t , d i f f e r e n c e s emerged due to d i f f e r e n t i a l e x t i n c t i o n r a t e s . NaCl i n t a k e was g r e a t e r than Compound i n t a k e i n f i v e of s i x animals and s l i g h t l y lower i n one (q = 4-46), while S a c c h a r i n and Compound consumption d i d not d i f f e r . Again note the c r o s s o v e r e f f e c t - However, the e f f e c t o c c u r r e d i n o n l y f o u r of s i x 50 animals, while being r e v e r s e d i n two o t h e r s . B C 1 2 3 4 5 TRIALS F i g u r e 2-D. C o n d i t i o n i n g and e x t i n c t i o n f l u i d i n t a k e f o r Group 4. See F i g u r e 1-A f o r a b s c i s s a l a b e l i n g . F i l l e d symbols re p r e s e n t water ( # ) , Coffee ( • ) , Vinegar ( • ) , Compound ( ) / and NaCl+Saccharin compound ( 0 ) . U n f i l l e d symbols show corr e s p o n d i n g water i n t a k e f o r the f i r s t e x t i n c t i o n p r e s e n t a t i o n of each s o l u t i o n ( f i l l e d symbols) . Figure 2-D shows the r e s u l t s f o r Group 4. The r e s u l t s are very s i m i l a r t o those of Groups 1, 2, and 3. The Compound of 51 C o f f e e and Vinegar was avoided to an extent s i m i l a r to the i n d i v i d u a l elements. The l a c k of any s u b s t a n t i a l r e d u c t i o n i n i n t a k e of the novel Compound, NaCl+ S a c c h a r i n , c l e a r l y shows the s p e c i f i c i t y of the reduced i n t a k e o f the other t a s t e s o l u t i o n s . Intake of the Compound (NaCl+Saccharin) d u r i n g the f i r s t t e s t t r i a l was lower than c o n d i t i o n i n g day i n t a k e of Coffee (q = 5.8), but not Vinegar. The reduced i n t a k e o f C o f f e e and Vinegar was s i m i l a r to pr e v i o u s experiments (g = 15.02, 13.32; r e s p e c t i v e l y ) . Intake of the Coffee+Vinegar Compound d u r i n g the f i r s t t e s t t r i a l was reduced compared t o c o n d i t i o n i n g day i n t a k e of Cof f e e (g = 17.62) and Vinegar (g = 13.6). Compound i n t a k e during the f i r s t two t e s t t r i a l s was not d i f f e r e n t from C o f f e e . During the l a s t three t e s t t r i a l s C offee and Compound i n t a k e d i f f e r e d . Compound and Vinegar i n t a k e never d i f f e r e d during t e s t i n g . Again note the c r o s s o v e r e f f e c t . However, as with Group 3, t h i s e f f e c t was seen i n only f o u r animals. Summary of R e s u l t s When two t a s t e s o l u t i o n s are i n d i v i d u a l l y p a i r e d with i l l n e s s and then compounded, the compound i s avoided as much as or more than the i n d i v i d u a l elements. A g e n e r a l neophobic r e a c t i o n cannot account f o r these r e s u l t s . 52 DISCUSSION The r e s u l t s c l e a r l y demonstrate t h a t , when two a v e r s i v e g u s t a t o r y cues are compounded, the compound i s t r e a t e d by the r a t s as being composed of a v e r s i v e elements and not simply as a n o v e l s o l u t i o n - C o n t r o l procedures (Group 4) r u l e out a g e n e r a l neophobic r e a c t i o n as being r e s p o n s i b l e f o r the reduced i n t a k e of the Compound. The r e s u l t s of Experiment II support the b a s i c c o n c l u s i o n s of Experiment I: that the r a t s ' g u s t a t o r y system i s capable of responding i n complex ways to a compound gus t a t o r y s t i m u l u s and i t s r e s p e c t i v e elements. These data accord f a i r l y w e l l with an e x t e n s i v e l i t e r a t u r e c o n c erning the combination of s e p a r a t e l y c o n d i t i o n e d s t i m u l u s elements (cf. Weiss, 1972). A major f i n d i n g concerning compound st i m u l u s c o n t r o l i s the summation e f f e c t . Suppressive summation i n t a s t e a v e r s i o n c o n d i t i o n i n g would be demonstrated when two f l a v o r s , s e p a r a t e l y a s s o c i a t e d with t o x i c o s i s and then put i n compound, produce suppression g r e a t e r than the s u p p r e s s i o n to e i t h e r f l a v o r (Weiss, 1972). Weiss (1972) analyzed the r e s u l t s of numerous ( p r i m a r i l y operant c o n d i t i o n i n g ) experiments concerned with the compounding of s t i m u l u s elements, and concluded t h a t the elements and compound l i e on a s t i m u l u s dimension which c o n t r o l s responding: [A] composite continuum i s d e f i n e d by the on-off s t a t e s of a l l r e l e v a n t d i s c r i m i n a t i v e or c o n d i t i o n e d s t i m u l i , one continuum extreme anchored to the a i l - o f f s t a t e , the other to a l l - o n . The p o i n t s between these continuum extremes are s c a l e d with r e f e r e n c e to the number of elements common to each . . ., the number of p o i n t s on any composite s c a l e being equal to the number of independently c o n d i t i o n e d SDs, or CSs, plus one (Weiss, 1969, pp. 22-23). 53 .Responding i s high i f the a l l - o n (e.g., a compound of two c o n t r o l l i n g s t i m u l i ) end of the continuum i s presented to the animal, and low i f the a i l - o f f (no c o n t r o l l i n g s t i m u l i present) end i s presented, l e v e l s of responding somewhere i n between occur when the middle of the continuum (§-<_., one stimulus) i s presented. Experiment I I f i t s i n t o t h i s f o r m u l a t i o n i f one views the absence of both s o l u t i o n s as the " a i l - o f f s t a t e " ; the presence of NaCl or S a c c h a r i n , f o r example, as a p o i n t i n between; and the presence of both NaCl and S a c c h a r i n as the " a l l - o n s t a t e " . Weiss*s f o r m u l a t i o n can be used to account f o r a d d i t i v e and s u p p r e s s i v e summation. The a l l - o n s t a t e , with the c o n c u r r e n t presence of two p o s i t i v e or two negative s t i m u l u s elements should r e s u l t i n g r e a t e r responding (or suppression of responding) than the presence of e i t h e r s t i m u l u s element alone. The r e s u l t s of Group 1 (NaCl+Saccharin Compound) are c o n s i s t e n t with a summation i n t e r p r e t a t i o n . During the second t e s t t r i a l Group 1 showed g r e a t e r s u p p r e s s i o n of Compound i n t a k e than s u p p r e s s i o n of i n t a k e of e i t h e r element. The c o n s i s t e n c y of t h i s f o r f i v e of s i x r a t s argues f o r i t s r e l i a b i l i t y . Because of the degree of suppression of i n t a k e of the t a s t e elements a summation e f f e c t would not be expected during the f i r s t t e s t t r i a l f o r Group 1. Intake of the elements was a t such low l e v e l s t h a t f u r t h e r r e d u c t i o n i n compound i n t a k e was i m p o s s i b l e ( i . e . , a f l o o r e f f e c t ) . The r e s u l t s of Group 2 (NaCl+Saccharin compound) suggested a s u p p r e s s i v e summation e f f e c t , but the seguence of s o l u t i o n p r e s e n t a t i o n d u r i n g t e s t i n g does not allow 54 f o r a f i n a l c o n c l u s i o n . The reason(s) why Group 3 f a i l e d t o show an enhanced summation e f f e c t i s not c l e a r . Weiss has pointed out t h a t there are s t u d i e s (Weiss, 1971; Lawson, M a t t i s , & Pear, 1968) which suggest that d i s c r i m i n a t i o n t r a i n i n g with the absence of the c o n t r o l l i n g s t i m u l i i s e s s e n t i a l f o r a d d i t i v e (and probably suppressive) summation. Weiss (1971) d i d an experiment i n which a tone and l i g h t s i g n a l l e d a v a i l a b i l i t y of reinforcement when s e p a r a t e l y presented. The r a t s never experienced the absence of e i t h e r the tone or l i g h t , i . e . , no i n t e r t r i a l i n t e r v a l or other s t i m u l i s i g n a l i n g the n o n - a v a i l a b i l i t y of r e i n f o r c e m e n t . The r a t s were even removed from the box i n the presence of e i t h e r the tone or the l i g h t . A d d i t i v e summation was not ob t a i n e d . Weiss maintains t h a t the absence of the c o n t r o l l i n g s t i m u l i i n the c o n d i t i o n i n g s i t u a t i o n i s probably e s s e n t i a l to the o b t a i n i n g of a d d i t i v e summation. Van Houten & Rudolph (1971) re p o r t e d s i m i l a r r e s u l t s with a s u p p r e s s i v e summation procedure. Although f o r Groups 1, 2, and 4 water s i g n a l l e d the absence of the a v e r s i v e elements, i t may not have been a s u f f i c i e n t l y s a l i e n t cue. The f a c t t h a t the r a t s had been exposed t o water s i n c e b i r t h , and the home cage t e s t i n g procedure, c o u l d have a t t e n u a t e d any l a r g e d i s c r i m i n a t i v e e f f e c t s o f the absence of the a v e r s i v e t a s t e elements. Reasoning along these l i n e s one might p r e d i c t poorer su p p r e s s i v e summation because of the l a c k of a c l e a r a i l - o f f s t a t e . I f a t h i r d novel t a s t e s o l u t i o n was i n t r o d u c e d during t r a i n i n g and never f o l l o w e d by s i c k n e s s , a c l e a r e r a i l - o f f s t a t e would presumably be e s t a b l i s h e d and thus 55 perhaps a c l e a r e r demonstration o f sup p r e s s i v e summation- Group 3 was an attempt to produce a b e t t e r o f f - s t a t e by p r e s e n t i n g Vinegar as " s a f e " during c o n d i t i o n i n g ; the r e s u l t s f o r t h i s group, however, were e g u i v o c a l . There i s o f t e n c o n s i d e r a b l e v a r i a b i l i t y i n the attainment of c l e a r a d d i t i v e or suppressive summation i n t r a d i t i o n a l paradigms. For example, Emurian & Weiss (1972) demonstrated a d d i t i v e summation i n a f r e e operant shock-avoidance schedule using a tone or a l i g h t presented i n an i r r e g u l a r order to s i g n a l the shock avoidance contingency, while the absence o f tone and l i g h t s i g n a l l e d shock f r e e p e r i o d s . Although a d d i t i v e summation was demonstrated t o the t o n e + l i g h t combination, a c l o s e look at the data over the 28 t e s t s e s s i o n s i n d i c a t e s a good d e a l of v a r i a b i l i t y i n the summation e f f e c t . During some t e s t s e s s i o n s no a d d i t i v e summation e f f e c t could be seen. The c r o s s o v e r of the e x t i n c t i o n curves o f a l l groups i s a r a t h e r c l e a r example of averaging (Weiss, 1972). According to Weiss's (1972) model of s t i m u l u s compounding, a s t i m u l u s c o n t r o l l i n g one response tendency (e-jg. , no responding) when compounded with a s t i m u l u s c o n t r o l l i n g another response tendency (e. c [ -, responding) should produce an i n t e r m e d i a t e response r a t e . T h i s presumably i s due to the c o n f l i c t i n g tendency at any given moment to respond or not to respond, thus r e s u l t i n g i n an i n t e r m e d i a t e amount of responding. Averaging has been demonstrated i n t r a d i t i o n a l paradigms by s e v e r a l r e s e a r c h e r s ( C o r n e l l 8 Strub, 1965; Weiss, 1967, 1969, 1972; Pavlov, 1927). Averaging would be evidenced i n t a s t e a v e r s i o n l e a r n i n g i f 56 a " s a f e " s o l u t i o n were put i n compound with an "unsafe" s o l u t i o n , and the r e s u l t i n g consumption was i n t e r m e d i a t e between consumption of the s a f e and the unsafe s o l u t i o n . F i g u r e s 2-A and 2-B show that consumption of the NaCl s o l u t i o n had returned to b a s e l i n e l e v e l s by the t h i r d t e s t t r i a l , while S a c c h a r i n i n t a k e had not. Consumption of the Compound would then be p r e d i c t e d to f a l l somewhere i n between the i n t a k e of Sac c h a r i n and NaCl, which i t does. The r e s u l t s f o r Group 3 (Figure 2-C) shows a s i m i l a r averaging e f f e c t . F i g u r e 2-D (Group 4) a l s o shows t h i s e f f e c t f o r C o f f e e , Vinegar, and the compound of these. The present r e s u l t s bear on the concept of " c o n f i g u r i n g " , as d i s c u s s e d by Razran (1965). Razran d e s c r i b e s the r e s u l t s of s e v e r a l Russian experiments t h a t demonstrate t h a t c o n d i t i o n i n g o c c u r s not only t o the elements of a compound, but a l s o to the compound p.er se. Razran maintains t h a t the compound forms a separate a s s o c i a t i o n with the unconditioned s t i m u l u s . A comparison of F i g u r e s 1-A, 1-B, 1-C, and 1-D as w e l l as panels 1 and 2 of Fig u r e 1-E (Experiments IA & IB) with F i g u r e s 2-A, 2-B, 2-C, and 2-D (Experiment II) show a s t r i k i n g d i f f e r e n c e i n the r e s u l t s of the two experiments. E x t i n c t i o n of avoidance of the Compound i n Experiments IA and IB was slower r e l a t i v e t o the e x t i n c t i o n of avoidance of the elements. E x t i n c t i o n of avoidance o f the Compound and elements of Experiment II showed c o n s i d e r a b l e o v e r l a p . T h i s i s c o n s i s t e n t with Razran's i n t e r p r e t a t i o n - When a compound i s s p e c i f i c a l l y f o l l o w e d by an i l l n e s s UCS, an a s s o c i a t i o n i s formed not only between the elements and the UCS, but a l s o between the compound and the UCS. T h i s n o t i o n i s supported by the r e s u l t s of Experiment IA and IB. 57 Consumption of both elements had returned to b a s e l i n e l e v e l s , but consumption of the Compound was s t i l l c o n s i d e r a b l y suppressed- Thus, suppression of Compound s o l u t i o n i n t a k e was due t o more than j u s t the c o n d i t i o n i n g that o c c u r r e d to the separate t a s t e elements- The Compound _>er se suppressed f l u i d consumption independently of the su p p r e s s i o n of i n t a k e of each element. The e x t i n c t i o n data of Experiment II showed t h a t s p e c i f i c c o n d i t i o n i n g of avoidance of the elements but not the Compound r e s u l t e d i n much more r a p i d e x t i n c t i o n of avoidance of the Compound r e l a t i v e to the elements-Baker (1969) a l s o has argued f o r separate CS-DCS conn e c t i o n s between the elements of the compound and the elements together. Weiss (1972) does not deal with element s t r e n g t h as a f u n c t i o n of s p e c i f i c compound or element c o n d i t i o n i n g . However, the s t r o n g e r c o n d i t i o n i n g of behavior to the compound, r e l a t i v e to c o n d i t i o n i n g of behavior t o the elements when the compound CS i s followed by the UCS, does not appear incompatible with h i s f o r m u l a t i o n . E e s c o r l a (1972, 1973) has a l s o argued that c o n d i t i o n i n g of a compound of two s t i m u l i generates a "unique" stimulus element t h a t i s not present when the s t i m u l u s elements are c o n d i t i o n e d s e p a r a t e l y . He suggests c o n f i g u r a l c o n d i t i o n i n g can occur i f a compound i s fo l l o w e d by a r e i n f o r c e r , while i t s member elements are not. The procedure of a r r a n g i n g reinforcement a f t e r the compound, but not i t s elements a l o n e , produces c o n t r o l of behavior by the unique s t i m u l u s formed by the two elements i n compound. T h i s unique s t i m u l u s element accounts f o r a l l of the p o s i t i v e a s s o c i a t i v e s t r e n q t h while the elements become i n h i b i t o r y . T h i s i s c o n s i s t e n t with 58 the p o s i t i o n of both Razran (1965) and Baker (1 968) concerning the nature of c o n f i g u r a l c o n d i t i o n i n g . However, th e r e i s some disagreement r e g a r d i n g the n e c e s s i t y of d i f f e r e n t i a l r e i n f o r c e m e n t i n e s t a b l i s h i n g c o n f i g u r a l c o n d i t i o n i n g (see Booth & Hammond, 1971). 59 EXPERIMENT I I I COMPOUND CONDITIONING WITH~FAMillAR AND UM M I L l M TASTE ELEMENTS A t a s t e t h a t i s f a m i l i a r t o a r a t i s more r e s i s t a n t to a v e r s i o n c o n d i t i o n i n g than one that i s novel at the time of c o n d i t i o n i n g (Kalat & Rozin, 1973)- T h i s e f f e c t i s s i m i l i a r to the w e l l documented " l a t e n t i n h i b i t i o n " e f f e c t (Lubow, 1975). By preexposing a t a s t e one presumably i s making i t a l e s s s a l i e n t , l e s s well attended t o , or l e s s l i k e l y a source of s i c k n e s s . Thus, one would expect c o n d i t i o n i n g t o the no v e l element of a compound of novel and f a m i l i a r f l a v o r s to "overshadow" c o n d i t i o n i n g to the f a m i l i a r element. Experiment I I I was designed to t e s t t h i s n o t i o n . METHOD s u b j e c t s Group 1 c o n s i s t e d of thr e e male and thr e e female second g e n e r a t i o n c r o s s b r e e d s . These r a t s had p r e v i o u s l y served i n an experiment i n which they were given s e v e r a l weeks of preference t e s t i n g between tap water and 0.9% NaCl. Group 2 c o n s i s t e d of th r e e male and three female second and t h i r d g e n e r a t i o n c r o s s b r e e d s . Procedure Table 4 shows the s o l u t i o n s presented to each group i n each major phase of Experiment I I I . Group 1 s u b j e c t s were exposed t o three s u c c e s s i v e days of 10 min access to 1.0% NaCl f o l l o w e d by 10 min access to tap water. T h i s was followed by t h r e e days of 60 a c c e s s to tap water only f o r 10 min per day. On ,tfae f o l l o w i n g day a compound s o l u t i o n of 1.0% NaCl + 0-25% S a c c h a r i n was presented f o r 10 min, f o l l o w e d by a standard i n j e c t i o n of L i C l . TABLE 4 Summary of procedure f o r each group, showing t a s t e s o l u t i o n s presented i n each of the three major phases of Experiment I I I . Experimental phase C o n d i t i o n i n g ( S o l u t i o n - L i C l E x t i n c t i o n Group Preexposure P a i r i n g ) (Test t r i a l s ) S a c c h a r i n S a c c h a r i n + 1 NaCl + NaCl NaCl Saccharin NaCl Saccharin (1/2 group) Sac c h a r i n + 2 Saccharin + NaCl (1/2 group) NaCl NaCl Sac c h a r i n A l l r a t s r e c e i v e d 10 min access to water on the f o l l o w i n g day. T e s t i n g began on the next day. The Compound, NaCl, and Saccharin s o l u t i o n s were presented i n a counterbalanced order over three day t e s t i n g c y c l e s . During the t h i r d , f o u r t h , and f i f t h t e s t s only the Compound and S a c c h a r i n were presented. The Compound was presented to a l l animals on the f i r s t day, and S a c c h a r i n on the second day f o r each t e s t c y c l e of the l a s t t h r e e t e s t seguences. Group 2 s u b j e c t s r e c e i v e d treatment s i m i l a r to t h a t of Group 1 with some e x c e p t i o n s . One-half of the group (2 males and 1 female) were preexposed to a 0.25% S a c c h a r i n s o l u t i o n f o r 10 days- The other h a l f (2 females and 1 male) r e c e i v e d 10 days 61 preexposure t o a 1-0% NaCl s o l u t i o n - On the day f o l l o w i n g the preexposure p e r i o d , the s u b j e c t s r e c e i v e d 10 min access to water- On the f o l l o w i n g day, a l l s u b j e c t s r e c e i v e d 10 min access t o a compound s o l u t i o n of 1-0% NaCl+0.25% Sac c h a r i n f o l l o w e d w i t h i n 10 min by a standard i n j e c t i o n of L i C l - Water was given on the next day- Then the t e s t i n g seguence began. A l l s o l u t i o n s , (Compound, NaCl, and Saccharin) were presented during t h r e e day t e s t c y c l e s , with each r a t r e c e i v i n g a d i f f e r e n t order of s o l u t i o n p r e s e n t a t i o n . Data P r e s e n t a t i o n and A n a l y s i s T h i s aspect of the experiment was s i m i l a r to previous experiments. A repeated measures t - t e s t was used to assess i n t a k e r e d u c t i o n of the preexposed s o l u t i o n . A l l other comparisons were made with Tukey's HSD t e s t . RESULTS The r e s u l t s f o r Group 1 are presented i n F i g u r e 3-A. During the f i r s t t e s t t r i a l , i n t a k e of the Compound was reduced from c o n d i t i o n i n g day with i n t a k e r e d u c t i o n s between 40% and 99% f o r d i f f e r e n t s u b j e c t s (g = 7.09). Intake o f S a c c h a r i n was s i m i l a r l y reduced from i n t a k e of the Compound on c o n d i t i o n i n g day. Intake of NaCl was a l s o reduced from i t s p r e c o n d i t i o n i n g l e v e l (t = 2-64). NaCl i n t a k e r e d u c t i o n s , however, were s m a l l . NaCl i n t a k e was c o n s i d e r a b l y g r e a t e r d u r i n g the f i r s t t e s t t r i a l than i n t a k e of e i t h e r the Compound (g = 10.8) or S a c c h a r i n (g = 11.0). Intake of the Compound and Saccharin d i d not d i f f e r . 62 1 i i i i i i . B C 1 2 3 4 TRIALS F i g u r e 3-A- Preexposure, c o n d i t i o n i n g , and e x t i n c t i o n f l u i d i n t a k e f o r Group 1. See F i g u r e 1-A f o r a b s c i s s a l a b e l i n g and e x p l a n a t i o n of symbols. The e x t i n c t i o n curves f o r avoidance of the Compound and Sa c c h a r i n f o l l o w a s i m i l a r course, d i v e r g i n g only d u r i n g the t h i r d t e s t i n f i v e of s i x animals. T h i s divergence c o u l d e a s i l y be an order e f f e c t because the Compound was presented to a l l animals on one day, and f o l l o w e d the next day by S a c c h a r i n . Although i n t a k e of the compound and Saccharin were not reduced ( r e l a t i v e t o c o n d i t i o n i n g day l e v e l s ) a f t e r the f i r s t t e s t , consumption s t i l l was suppressed i n some animals. NaCl i n t a k e 63 r e t u r n e d to p r e c o n d i t i o n i n g l e v e l s by the second t r i a l . Intake of the Compound and S a c c h a r i n remained reduced r e l a t i v e to NaCl i n t a k e during the second t e s t . The r e s u l t s f o r Group 2 are shown i n F i g u r e 3-B. Data f o r each sub-group are presented s e p a r a t e l y a c c o r d i n g t o the s t i m u l u s r e c e i v e d during preexposure. The f i l l e d symbols r e p r e s e n t intake by the three animals given S a c c h a r i n d u r i n g preexposure. No s t a t i s t i c a l a n a l y s i s was done because of the s m a l l number of s u b j e c t s . F o l l o w i n g Compound-LiCl p a i r i n g a l l t h r e e animals showed Compound i n t a k e r e d u c t i o n s of 50% to 70%. NaCl i n t a k e { u n f a m i l i a r s o l u t i o n ) was reduced by s i m i l a r amounts. Saccharin i n t a k e , the f a m i l i a r s o l u t i o n , was reduced by l e s s e r amounts i n every animal. S a c c h a r i n consumption was approximately twice t h a t of the Compound and NaCl i n every animal. Recovery of consumption d u r i n g e x t i n c t i o n was very r a p i d f o r NaCl which i s c o n t r a r y to the r e s u l t s of Group 1 ( i . e., S a c c h a r i n i n t a k e recovered s l o w l y ) . NaCl i n t a k e c l e a r l y exceeded Compound i n t a k e i n every animal dur i n g the second t e s t by 4 to 9 ml. S a c c h a r i n i n t a k e recovered to b a s e l i n e l e v e l s on the second t e s t t r i a l . Compound i n t a k e during e x t i n c t i o n remained reduced from c o n d i t i o n i n g day l e v e l s i n every animal. The open symbols i n Figure 3-B r e p r e s e n t i n t a k e of the t h r e e animals t h a t were preexposed t o NaCl. These r e s u l t s are s i m i l a r to the r e s u l t s of Group 1. Compound i n t a k e f o l l o w i n g t o x i c o s i s dropped i n a l l animals to a mean of 2.6 ml. There were no c o n s i s t e n t d i f f e r e n c e s between Compound and S a c c h a r i n i n t a k e d u r i n g t e s t i n g . Intake of the f a m i l i a r s o l u t i o n , NaCl, dropped \ 2-I I .. I L I I I B C 1 2 3 4 TRIALS F i g u r e 3-B. Preexposure, c o n d i t i o n i n g , and e x t i n c t i o n f l u i d i n t a k e f o r Group 2.' Data f o r each subgroup are presented s e p a r a t e l y . F i l l e d symbols correspond to s u b j e c t s preexposed t o Sa c c h a r i n ( H ) • Other f i l l e d symbols are water ( ^ ) , NaCl a n d the Compound ( 0 ) « Open symbols correspond to s u b j e c t s preexposed to NaCl (/\) . Other open symbols are water ( Q ) , S a c c h a r i n ( Q ) , and the Compound See F i g u r e 1-A f o r a b s c i s s a l a b e l i n g . f o l l o w i n g c o n d i t i o n i n g i n every animal, but NaCl i n t a k e g r e a t l y exceeded Compound or Sa c c h a r i n i n t a k e -Summary of Re s u l t s LICL p o i s o n i n g f o l l o w i n g p r e s e n t a t i o n of a novel t a s t e 65 s o l u t i o n i n compound with a f a m i l i l a r t a s t e s o l u t i o n w i l l r e s u l t i n avoidance of the compound by the r a t being c o n t r o l l e d by the no v e l t a s t e element-DISCDSSION These data show c o n v i n c i n g l y t h a t the r a t can d e t e c t a novel s o l u t i o n i n compound and can respond with the a p p r o p r i a t e avoidance behavior even when the element i s subseguently separated from t h a t compound. The f a m i l i a r s o l u t i o n was not avoided to any e x t e n t r e l a t i v e to the u n f a m i l i a r s o l u t i o n i n e i t h e r group. Other r e s e a r c h e r s u s i n g s i n g l e s o l u t i o n designs have a l s o found t h a t b r i e f p r i o r exposure to a t a s t e s t i m u l u s attenuated i t s c o n d i t i o n a b i l i t y (Kalat S Rozin; 1971; McLaurin, F a r l e y , & Scarborough, 1963; Revusky & Bedarf, 1967; W i t t l i n & B r o o k s h i r e , 1968; Domjan, 1972; Revusky & G a r c i a , 1970; Vogel & Clody, 1972). The present r e s u l t s show t h a t the same e f f e c t occurs when the f a m i l i a r t a s t e i s part of a compound. Group 1 r a t s showed a s m a l l d e c l i n e i n f a m i l i a r s o l u t i o n i n t a k e from p r e c o n d i t i o n i n g l e v e l s during the f i r s t t e s t . T h i s s m a l l d e c l i n e was no doubt due t o the e x t e n s i v e preexposure to NaCl that Group 1 s u b j e c t s r e c e i v e d . In l i n e with t h i s n o t i o n i s the l a r g e r amount of c o n d i t i o n i n g t o the preexposed s o l u t i o n by Group 2 s u b j e c t s . Because preexposure f o r these s u b j e c t s was f o r only 10 days, r e l a t i v e l y more c o n d i t i o n i n g t o the preexposed s t i m u l u s would be p r e d i c t e d (Fenwick, Mikulka, & K l e i n , 1975). Another i n t e r e s t i n g aspect o f these r e s u l t s concerns the 6 6 amount of suppression of S a c c h a r i n i n t a k e - Compare the amount of s u p p r e s s i o n of S a c c h a r i n i n t a k e i n Experiment IB (Group 1), i n which a l l s u b j e c t s had one Compound-LiCl p a i r i n g , with the r e s u l t s of the present experiment (Group 1), i n which the r a t s a l s o had one Compound-LiCl p a i r i n g - Although such a between groups comparison i s not e n t i r e l y a p p r o p r i a t e , i t i s c e r t a i n l y s u g g e s t i v e of an enhancement of c o n d i t i o n i n g to the S a c c h a r i n s o l u t i o n - In Experiment IB i n t a k e of Saccharin d i f f e r e d from i n t a k e of the Compound; here i n t a k e of Saccharin and the Compound were very s i m i l a r . A l s o note t h a t S a c c h a r i n i n t a k e i n Experiment IB averaged 5-68 ml even though Compound i n t a k e was e s s e n t i a l l y zero- In the present experiment Group 1 r a t s 1 S a c c h a r i n i n t a k e averaged 2.67 ml. In f a c t , the S a c c h a r i n i n t a k e of only one animal i n Group 1 o v e r l a p s with the i n t a k e of S a c c h a r i n i n Experiment IB- The r e s u l t s of Group 2 of the present experiment a l s o suggest an enhancement of c o n d i t i o n i n g •to the novel s o l u t i o n - I t appears t h a t the presence of the f a m i l i a r s o l u t i o n i n compound with a novel s o l u t i o n enhances the c o n d i t i o n i n g t o the n o v e l s o l u t i o n r e l a t i v e to c o n d i t i o n i n g t o a novel s o l u t i o n when i n compound with another novel s o l u t i o n . T h i s e f f e c t i s c o n s i s t e n t with Revusky's (1971) notion concerning the f o r m a t i o n of t a s t e a v e r s i o n s , ihen two novel s o l u t i o n s are presented the r a t must attend to both as p o s s i b l e sources of malaise, thus causing a decreased amount of c o n d i t i o n i n g t o e i t h e r . I f , however, one element of the compound i s " s a f e " then the r a t i s r e l a t i v e l y f r e e t o i g n o r e i t and a t t e n d more to the novel s o l u t i o n as the source of malaise. The apparent enhanced c o n d i t i o n i n g of Saccharin i n compound 67 with a f a m i l i a r s o l u t i o n i s a l s o p r e d i c t a b l e from Wagner and E e s c o r l a ' s (1972) model of P a v l o v i a n c o n d i t i o n i n g . In f a c t Wagner (1969) r e p o r t s an experiment using r a t s i n which one element (tone) of a compound s t i m u l u s was not f o l l o w e d by re i n f o r c e m e n t , while t h a t element i n compound with another added element ( l i g h t ) was r e i n f o r c e d - Wagner found t h a t c o n d i t i o n i n g t o the added element, the l i g h t , was enhanced r e l a t i v e to c o n d i t i o n i n g i n a group i n which the l i g h t was j u s t r e i n f o r c e d i n compound with the tone which had not had p r i o r n o n r e i n f o r c e d exposures. Wagner concluded t h a t n o n r e i n f o r c e d exposure t o the tone made i t l e s s c o n d i t i o n a b l e . Thus, during compound c o n d i t i o n i n g the novel s t i m u l u s element c o n t r o l l e d behavior t o a g r e a t e r degree than i f compounded with another novel element. 68 JI1I1SJENT IV COMPOUND CONDITIONING WITH FAMILIAR i S A J J l l M S JSSIEi TASTES Experiment IV was a s y s t e m a t i c follow-up of the suggestion of response averaging found i n Experiment IA. Averaging, as p r e v i o u s l y noted, occurs when a s t i m u l u s c o n t r o l l i n g one l e v e l of responding, put i n compound with a s t i m u l u s c o n t r o l l i n g another l e v e l , c o n t r o l s a l e v e l of responding i n t e r m e d i a t e to the response l e v e l s c o n t r o l l e d by the elements (Weiss, 1972). There have been numerous demonstrations of t h i s b a s i c phenomenon (Pavlov, 1927; R e s c o r l a , 1969; Redberg S Black, 1969; C o r n e l l and Strub, 1965; Weiss, 1967). Weiss' (1972) a n a l y s i s p r e d i c t s response averaging when two s t i m u l i c o n t r o l l i n g widely d i s c r e p a n t r a t e s are compounded. Experiment IV extends the phenomenon of averaging to the g u s t a t o r y system of the r a t . The experiment was designed to t e s t the e f f e c t s of combining an a v e r s i v e s o l u t i o n ( p r e v i o u s l y p a i r e d with t o x i c o s i s ) i n compound with a f a m i l i a r s o l u t i o n not p a i r e d with t o x i c o s i s or a s o l u t i o n s p e c i f i c a l l y e s t a b l i s h e d as " s a f e " through d i f f e r e n t i a l c o n d i t i o n i n g . I f a f a m i l i a r (safe) s o l u t i o n i s put i n compound with an a v e r s i v e s o l u t i o n , the i n t a k e of the compound should be i n t e r m e d i a t e between the i n t a k e of the two s o l u t i o n s presented s e p a r a t e l y . METHOD Subj e c t s Six r a t s s i m i l a r to those used i n Experiment I I I , Group 1 69 served as s u b j e c t s . These r a t s had served i n a previous experiment along with those of Group 1 i n Experiment I I I . Procedure Table 5 shows the s o l u t i o n s presented during each major phase of the experiment. The p r e l i m i n a r y exposure t o NaCl and TABLE 5 Summary of procedure showing t a s t e s o l u t i o n s presented i n each of the th r e e major phases of Experiment IV. Experimental phase C o n d i t i o n i n g ( S o l u t i o n - L i C l E x t i n c t i o n C o n d i t i o n Preexposure p a i r i n g ) (Test t r i a l s ) S a ccharin + NaCl S a c c h a r i n - L i C l NaCl NaCl Saccharin S a c c h a r i n + N a C l - L i C l NaCl Sa c c h a r i n NaCl (not paired) S a c c h a r i n water was i d e n t i c a l to Experiment I I I , Group 1. On the c o n d i t i o n i n g day, a l l r a t s r e c e i v e d 10 min access t o Sac c h a r i n f o l l o w e d by an i n j e c t i o n of L i C l . On the f o l l o w i n g day, a l l r a t s were exposed t o a compound s o l u t i o n c o n s i s t i n g of 1.0% NaCl and 0.25% S a c c h a r i n . On the next t e s t i n g day one-half of the r a t s were exposed t o NaCl, the other h a l f to S a c c h a r i n . T h i s was 70 rev e r s e d the f o l l o w i n g day. T h i s sequence was repeated twice and then NaCl was dropped from the seguence. Fo l l o w i n g e x t i n c t i o n of avoidance of a l l s o l u t i o n s the r a t s were next (Condition 2) given 10 min access to water each day f o r s e v e r a l days. Then NaCl was presented f o r 10 min fo l l o w e d by L i C l . On the f o l l o w i n g day S a c c h a r i n was a v a i l a b l e f o r 10 min f o l l o w e d by 10 min access t o water- T h i s sequence was repeated f o u r times u n t i l NaCl i n t a k e was suppressed i n a l l animals-F o l l o w i n g the l a s t N a C l - L i C l p a i r i n g Saccharin was presented f o r two days, f o l l o w e d by NaCl f o r two days- The c r i t i c a l t e s t with the Compound occurred on the next day, followed by a day with NaCl a v a i l a b l e and a day with S a c c h a r i n a v a i l a b l e . T h i s c y c l e of Compound, NaCl, and S a c c h a r i n a v a i l a b i l i t y was repeated once more. Ten min access to tap water f o l l o w e d each of these t e s t s o l u t i o n p r e s e n t a t i o n s . S a c c h a r i n was then dropped from the t e s t i n g c y c l e which was repeated twice more f o l l o w e d by NaCl on the l a s t t e s t day. The l a s t two t e s t seguences and the l a s t NaCl p r e s e n t a t i o n were not fo l l o w e d by 10 min access to tap water. Data P r e s e n t a t i o n and A n a l y s i s T h i s aspect of the experiment was s i m i l a r to pr e v i o u s experiments. RESULTS The r e s u l t s f o r C o n d i t i o n 1 are presented i n F i g u r e 4-A. During the f i r s t t e s t c y c l e i n t a k e of NaCl i n compound with S a c c h a r i n was c o n s i d e r a b l y l e s s than i n t a k e of NaCl (g = 12.25), 71 with i n t a k e r e d u c t i o n s ranging from 60% to 87%. NaCl i n t a k e d u r i n g the f i r s t t e s t d i d not d i f f e r from p r e c o n d i t i o n i n g l e v e l s . During the f i r s t t e s t i n t a k e of the Compound was more than Saccharin i n every animal. However, s i g n i f i c a n c e was not reached. Compound i n t a k e , although somewhat reduced i n f i v e of s i x animals, d i d not d i f f e r from c o n d i t i o n i n g day i n t a k e o f S a c c h a r i n . S a c c h a r i n i n t a k e d u r i n g the f i r s t t e s t was l e s s than i n t a k e of Sac c h a r i n on the c o n d i t i o n i n g day (g •= 6.38). The e x t i n c t i o n data showed c l e a r l y t h a t avoidance of Sacc h a r i n e x t i n g u i s h e d more s l o w l y than avoidance of the Compound i n every animal. S a c c h a r i n i n t a k e r e l a t i v e to i t s i n t a k e on the c o n d i t i o n i n g day was reduced i n only t h r e e r a t s on the second e x t i n c t i o n t r i a l . The r e s u l t s of C o n d i t i o n 2 were s i m i l a r t o those of the f i r s t procedure. F i g u r e 4-B presents these data. During the f i r s t t e s t c y c l e i n t a k e of S a c c h a r i n i n compound with NaCl was reduced r e l a t i v e t o i n t a k e of Sac c h a r i n (g = 7.89). Intake r e d u c t i o n s ranged from 40% to 90%. Compound i n t a k e was a l s o g r e a t e r than NaCl i n t a k e on the day f o l l o w i n g the f i r s t Compound t e s t day (g = 4.10). A l l animals showed g r e a t e r Compound than NaCl consumption. NaCl i n t a k e was reduced t o very low l e v e l s r e l a t i v e to NaCl i n t a k e on the f i r s t c o n d i t i o n i n g day. Saccharin consumption was unchanged. S a c c h a r i n i n t a k e showed no d e c l i n e a t anytime during c o n d i t i o n i n g or t e s t i n g . The second t e s t p r e s e n t a t i o n of the Compound produced e s s e n t i a l l y the same e f f e c t s as the f i r s t . Compound i n t a k e was s t i l l reduced r e l a t i v e to Saccharin i n t a k e i n every animal. 72 LI - J 1 I I t L_ B C 1 2 3 4 TRIALS F i g u r e 4-A. Preexposure, c o n d i t i o n i n g , and e x t i n c t i o n f l u i d i n t a k e f o r C o n d i t i o n 1. See F i g u r e 1-A f o r an e x p l a n a t i o n o f the symbols and a b s c i s s a l a b e l i n g . Compound i n t a k e was s t i l l g r e a t e r than NaCl i n t a k e i n every animal. NaCl i n t a k e remained very low. During the remaining r e s t s , consumption of NaCl and the Compound s o l u t i o n i n c r e a s e d . Summary, of Re s u l t s The r e s u l t s of C o n d i t i o n 1 c l e a r l y show that consumption of a Compound s o l u t i o n c o n s i s t i n g of a f a m i l i a r and an a v e r s i v e s o l u t i o n f a l l s a t a l e v e l i n t e r m e d i a t e between the i n t a k e of the 73 BICCCCB 1 2 3 4 5 6 7 TRIALS F i g u r e 4-B. D i f f e r e n t i a l c o n d i t i o n i n g and e x t i n c t i o n f l u i d i n t a k e i n C o n d i t i o n 2. Note the two p r e s e n t a t i o n s of NaCl i n e x t i n c t i o n before p r e s e n t a t i o n of the other s o l u t i o n s . See F i g u r e 1-A f o r a b s c i s s a l a b e l i n g and e x p l a n a t i o n of symbols. s o l u t i o n s presented s e p a r a t e l y . The r e s u l t s of C o n d i t i o n 2 t h a t "averaging" a l s o occurs i f a s o l u t i o n made e x p l i c i t l y " s a f e " i s compounded with an a v e r s i v e s o l u t i o n . show 74 DISCUSSION Averaging i n t a s t e a v e r s i o n l e a r n i n g f i t s i n w e l l with a l a r g e body of r e s e a r c h conducted with other more t r a d i t i o n a l cue-consequence systems (e.<_. , Weiss, 1972). The present r e s u l t s arque f o r a c o n d i t i o n e d i n h i b i t o r y i n t e r p r e t a t i o n of f l a v o r preexposure- The r a t a p p a r e n t l y l e a r n s t h a t a f l a v o r i s " s a f e " because of i t s not beinq f o l l o w e d by t o x i c o s i s . The s a f e s o l u t i o n then becomes a c o n d i t i o n e d i n h i b i t o r f o r avoidance behavior when p a i r e d with an a v e r s i v e s o l u t i o n . The present r e s u l t s along with the r e s u l t s of Experiment I I I conform t o R e s c o r l a ' s (1969) and Hearst's (1972) n o t i o n s r e g a r d i n g c o n d i t i o n e d i n h i b i t i o n . Hearst (1972) has d e a l t e x t e n s i v e l y with the problems i n v o l v e d i n l a b e l i n g a s t i m u l u s a c o n d i t i o n e d i n h i b i t o r . Hearst (1972) d e f i n e s a c o n d i t i o n e d i n h i b i t o r as: A s t i m u l u s t h a t , as a r e s u l t of some p r i o r a s s o c i a t i o n with a decrease i n the p r o b a b i l i t y of r e i n f o r c e m e n t , has a c g u i r e d the power to r e s t r a i n or prevent a b e h a v i o r a l e f f e c t that would otherwise occur (P. 34). Hearst suggests t h a t there are many ways o f d e t e c t i n g and measuring c o n d i t i o n e d i n h i b i t i o n , but the most a p p r o p r i a t e appear to be the combined cue (summation) and r e t a r d a t i o n of c o n d i t i o n i n g t e s t s . Hearst emphasizes t h a t as many i n d i c e s as p o s s i b l e should be used when determining i f a. s t i m u l u s i s a c o n d i t i o n e d i n h i b i t o r . I f only one method i s used t h e r e are problems of i n t e r p r e t a t i o n . For example, i f a r e t a r d a t i o n of 75 c o n d i t i o n i n g procedure shows that a s t i m u l u s i s r e s i s t a n t t o c o n d i t i o n i n g (due to some s p e c i f i c c o n d i t i o n i n g h i s t o r y ) , one c o u l d argue t h a t the sti m u l u s has simply become " l e s s s a l i e n t " r a t h e r than i n h i b i t o r y ( E e i s s S Wagner, 1971; E e s c o r l a , 1971; Halgren, 1974). A c o n d i t i o n e d i n h i b i t o r y i n t e r p r e t a t i o n would be strengthened i f the s t i m u l u s c o u l d be shown t o reduce responding i n a combined cues t e s t i n which the supposed i n h i b i t o r y s t i m u l u s i s superimposed on one t h a t c o n t r o l s a c e r t a i n response tendency. I f a st i m u l u s was simply l e s s s a l i e n t , then i t would not be expected t o d i s r u p t responding. Conversely, i f a st i m u l u s i s shown to reduce responding i n a combined cues t e s t , one could argue t h a t the p r i o r experience i n c r e a s e d a t t e n t i o n to that s t i m u l u s ( E e s c o r l a , 1969). T h i s enhanced a t t e n t i o n would lead to reduced responding i n the combined cues t e s t without r e q u i r i n g a c o n d i t i o n e d i n h i b i t o r y e x p l a n a t i o n . However, i f the s t i m u l u s was a l s o shown to be r e s i s t a n t to c o n d i t i o n i n g , then an enhanced a t t e n t i o n e x p l a n a t i o n would no longer be t e n a b l e (enhanced a t t e n t i o n should l e a d to q u i c k e r c o n d i t i o n i n g ) and a c o n d i t i o n e d i n h i b i t i o n i n t e r p r e t a t i o n would be strengthened. Experiment IV, C o n d i t i o n 2 meets Hearst's c r i t e r i o n of s p e c i f i c p r i o r c o n d i t i o n i n g with a d i s c r e t e s t i m u l u s as being necessary f o r the development of a c o n d i t i o n e d i n h i b i t o r . S a c c h a r i n was s p e c i f i c a l l y not p a i r e d with s i c k n e s s , while NaCl was. However, before Hearst would completely accept the r e s u l t s o f C o n d i t i o n 2 as evidence f o r c o n d i t i o n e d i n h i b i t i o n , a c o n t r o l f o r n o v e l t y would be r e g u i r e d . A group would be needed t h a t r e c e i v e d c o n d i t i o n i n g with NaCl and then a t e s t day with an NaCl+novel Sa c c h a r i n compound. T h i s group was not run because 76 the b a s i c concern of Experiment IV was to demonstrate averaging. However, i t seems l i k e l y that very l i t t l e of the NaCl+novel S a c c h a r i n compound would be consumed, e s p e c i a l l y i n view of the known neophobic r e a c t i o n to novel t a s t e s ( t h i s neophobia has a l r e a d y been mentioned r e g a r d i n g 0.25% S a c c h a r i n ) . C o n d i t i o n 1 contained procedures which conform to one of Hearst's other c o n t r o l procedures, i . e . , the h a b i t u a t e d - s t i m u l u s c o n d i t i o n i n which the s t i m u l u s i s preexposed without any UCS. The r e s u l t s of C o n d i t i o n 1 c l e a r l y showed an i n c r e a s e d consumption of the a v e r s i v e s o l u t i o n , S a c c h a r i n , when compounded with the preexposed s o l u t i o n , NaCl. One might argue t h a t because of the i n c r e a s e d Compound i n t a k e i n both C o n d i t i o n s 1 and 2 t h a t perhaps c o n d i t i o n e d i n h i b i t i o n d i d not occur. However, one co u l d e a s i l y argue the converse, i . e . , that i n both C o n d i t i o n s 1 and 2 the unpaired f l a v o r was a c o n d i t i o n e d i n h i b i t o r . In C o n d i t i o n 1 s u b j e c t s were not gi v e n p r i o r d i f f e r e n t i a l c o n d i t i o n i n g t o safe and a v e r s i v e t a s t e s o l u t i o n s as they were i n C o n d i t i o n 2. As p r e v i o u s l y mentioned Hearst c o n s i d e r s t h i s important, but he h i m s e l f notes that t h i s c r i t e r i o n i s somewhat " c a v a l i e r " (P.27). In f a c t the simple preexposure of a s t i m u l u s has o f t e n been l a b e l e d " l a t e n t i n h i b i t i o n " (see Lubow, 1973, and d i s c u s s i o n below). The above c o n s i d e r a t i o n s along with the well documented r e t a r d a t i o n - o f - l e a r n i n g e f f e c t with preexposed or " s a f e " t a s t e s t i m u l i (Kalat & E o z i n , 1973; Fenwick, Mikulka, and K l e i n , 1975; Vogel & Clody, 1972, as well as Experiment I I I and p a r t s of Experiments I of the present s e r i e s ) s t r o n g l y suggest a 77 c o n d i t i o n e d i n h i b i t o r y i n t e r p r e t a t i o n of the present r e s u l t s . Although the r e s u l t s of Experiments I I I ( l i t t l e c o n d i t i o n i n g to NaCl f o l l o w i n g preexposure) and C o n d i t i o n 1 of the present experiment argue f o r an i n t e r p r e t a t i o n of the preexposed t a s t e s t i m u l u s as a c o n d i t i o n e d i n h i b i t o r , other .explanations are a v a i l a b l e . One co u l d argue t h a t the Compound simply t a s t e s d i f f e r e n t . Thus i n c r e a s e d consumption would be due to a g e n e r a l i z a t i o n decrement and not to the presence of a c o n d i t i o n e d i n h i b i t o r . Arguing a g a i n s t a g e n e r a l i z a t i o n decrement i n t e r p r e t a t i o n are the r e s u l t s of Experiment I I . If the Compound t a s t e d d i f f e r e n t with r e s p e c t to the t a s t e elements, then one would not p r e d i c t the degree of a v e r s i o n to the Compound evidenced i n the r e s u l t s . A l s o , the r e s u l t s of Experiment I I I (Group 1) argue s t r o n g l y a g a i n s t such an i n t e r p r e t a t i o n . Only the Compound was p a i r e d with t o x i c o s i s i n Experiment I I I . Thus, i f NaCl i n compound with S a c c h a r i n a l t e r e d or attenuated the t a s t e of S a c c h a r i n , one would p r e d i c t t h a t S a c c h a r i n when presented s e p a r a t e l y would be avoided t o a l e s s e r degree than the Compound. T h i s was c l e a r l y not the case. The r e s u l t s of Group 2 (Experiment III) support t h i s c o n c l u s i o n . There has r e c e n t l y been some gues t i o n r e g a r d i n g the l a b e l i n g of a novel s o l u t i o n exposed to a r a t (without p a i r i n g i t with t o x i c o s i s ) as a c o n d i t i o n e d i n h i b i t o r (Best, 1975). K a l a t S Hozin (1973) as w e l l as ot h e r s ( S i e g e l , 1974; Nachman & Jones, 1974) have maintained t h a t a novel s o l u t i o n not followed by s i c k n e s s becomes a " s a f e " s o l u t i o n through a s s o c i a t i o n with s a f e conseguences (no s i c k n e s s ) . Thus, the preexposed s o l u t i o n becomes a c o n d i t i o n e d i n h i b i t o r of avoidance of that s o l u t i o n . 78 Others have taken a d i f f e r e n t view of s t i m u l u s preexposure. Three separate r e p o r t s ( R e s c o r l a , 1971; Reiss & Wagner, 1972; Halgren, 1974) have r e c e n t l y shown that preexposing a s t i m u l u s l e a d s to a r e d u c t i o n i n i t s subseguent a b i l i t y to a c t as e i t h e r a c o n d i t i o n e d i n h i b i t o r or a c o n d i t i o n e d e x c i t a t o r , thus s u p p o r t i n g a n o n - a s s o c i a t i v e (£.<_., reduced s a l i e n c e ) i n t e r p r e t a t i o n of the e f f e c t s of preexposure. R e s c o r l a ' s (1971) work i s r e p r e s e n t a t i v e . He used both a r e t a r d a t i o n - o f -c o n d i t i o n i n g and a summation t e s t with a preexposed s t i m u l u s . The preexposed s t i m u l u s was found to c o n d i t i o n l e s s r a p i d l y as e i t h e r an e x c i t a t o r y or i n h i b i t o r y s t i m u l u s . Also when the preexposed s t i m u l u s was compounded with a CS t h a t suppressed responding, t h e r e was no evidence o f any i n t e r f e r e n c e . R e s c o r l a as well as others i n t e r p r e t t h e i r r e s u l t s as support f o r the n o t i o n t h a t preexposure r e s u l t s i n a "reduced s a l i e n c e " and/or an "attention-decrement" b e h a v i o r a l process. Opposed to the above r e p o r t s of the n o n - i n h i b i t o r y f u n c t i o n s of a preexposed s t i m u l u s i s a r e p o r t by Kremer (1972) who found a summation e f f e c t . He found t h a t p a i r i n g a preexposed s t i m u l u s (white noise) with a CS f o r shock r e s u l t e d i n s i g n i f i c a n t l y g r e a t e r i n t e r f e r e n c e of responding than d i d a n o v e l s t i m u l u s . The d i s r u p t i o n of responding by the preexposed s t i m u l u s argues f o r an i n t e r p r e t a i o n of the preexposed CS as a c o n d i t i o n e d i n h i b i t o r . R e s c o r l a had i n f a c t found the o p p o s i t e , i . e . , the preexposed st i m u l u s d i d not d i s r u p t performance to any g r e a t e x t e n t . Kremer did not perform an experiment to see i f h i s preexposed s t i m u l u s compounded with the c o n d i t i o n e d CS would r e s u l t i n more r a p i d e x t i n c t i o n of response s u p p r e s s i o n than 79 p r e s e n t a t i o n of the c o n d i t i o n e d CS alone (as R e s c o r l a had done). However, from the r e s u l t s of Kreraer's compounding experiment, one would p r e d i c t more r a p i d e x t i n c t i o n of the compound of c o n d i t i o n e d CS+preexposed s t i m u l u s . Thus i t would appear that even i n the more " t r a d i t i o n a l " c o n d i t i o n i n g l i t e r a t u r e the concept of preexposure r e s u l t i n g i n " l o s s of s a l i e n c e " i s not f i r m l y e s t a b l i s h e d . Best. (1975) has r e c e n t l y claimed, using a t a s t e a v e r s i o n procedure, t h a t preexposure to s a l i n e a c t u a l l y reduces the l i k e l i h o o d of t h a t s o l u t i o n l a t e r becoming a c o n d i t i o n e d i n h i b i t o r . The f i r s t p art of Best's experiment showed enhanced pr e f e r e n c e f o r a s a l i n e s o l u t i o n that was presented immediately f o l l o w i n g access to an a v e r s i v e S a c c h a r i n s o l u t i o n . Best argued t h a t t h i s was evidence f o r c o n d i t i o n e d i n h i b i t i o n . Next he compared two groups of r a t s t h a t had r e c e i v e d the a v e r s i v e t a s t e s o l u t i o n f o l l o w e d by s a l i n e , except t h a t one group had a l s o r e c e i v e d two a d d i t i o n a l preexposures to s a l i n e . T h i s second group showed a reduced p r e f e r e n c e f o r s a l i n e compared to the f i r s t group when l a t e r t e s t e d i n a two b o t t l e ( s a l i n e vs water) pr e f e r e n c e t e s t . Best reasoned that i f preexposure r e s u l t s i n c o n d i t i o n e d i n h i b i t i o n , then t h i s second group should have shown an enhanced s a l i n e preference r e l a t i v e to the non-preexposed group. Thus, Best argued, preexposure a c t u a l l y i n t e r f e r e d with the preexposed t a s t e s o l u t i o n becoming a c o n d i t i o n e d i n h i b i t o r . T h i s of course i s d i r e c t l y c o n t r a r y to the concept of learned s a f e t y but compatible with a " l o s s of s a l i e n c e " argument. One c o u l d suggest t h a t although Best has demonstrated t h a t h i s procedure r e s u l t s i n an enhanced preference f o r s a l i n e , and by 80 h i s d e f i n i t i o n e s t a b l i s h e d s a l i n e as a c o n d i t i o n e d i n h i b i t o r , t h i s does not preclude h i s other procedures (preexposing s a l i n e a f t e r f a m i l i a r S a c c h a r i n p r e s e n t a t i o n ) from a l s o e s t a b l i s h i n g s a l i n e as a c o n d i t i o n e d i n h i b i t o r , although a l e s s e r one. In f a c t the two main t e s t s f o r c o n d i t i o n e d i n h i b i t i o n as set out by Hearst (1972) and R e s c o r l a and Wagner (1972), the r e t a r d a t i o n of l e a r n i n g and summation t e s t , were not a p p l i e d . The reason (s) f o r the reduced c o n d i t i o n e d i n h i b i t i o n seen i n the group that had been preexposed to s a l i n e p r i o r t o i t being put i n Best's c o n d i t i o n e d i n h i b i t i o n paradigm ( a v e r s i v e Saccharin s o l u t i o n f o l l o w e d by access to s a l i n e ) i s not c l e a r . However, i t may be premature to conclude t h a t i t was due t o an impairment of the c o n d i t i o n e d i n h i b i t o r y p r o p e r t i e s of the preexposed s a l i n e . I t i s c e r t a i n l y t r u e t h a t i f preexposing a t a s t e s t i m u l u s r e s u l t s i n l e a r n e d s a f e t y ( c o n d i t i o n e d i n h i b i t i o n ) , then preexposing a s t i m u l u s should r e s u l t i n enhanced i n h i b i t o r y p r o p e r t i e s . However, there are problems with Best's procedure. Davenport (1973) has shown that when r a t s are given s u c c e s s i v e exposures to s a l i n e i n the o n e - b o t t l e s i t u a t i o n , t h e i r preference f o r s a l i n e w i l l d e c l i n e . The s a l i n e preexposed group i n Best's experiment was placed under s i m i l a r c o n d i t i o n s . Thus, the preexposed group would have a d e c l i n i n g s a l i n e p r e f erence r e l a t i v e t o the non-preexposed group. T h i s d e c l i n i n g preference would then counteract the c o n d i t i o n e d i n h i b i t o r y p r o p e r t i e s of the preexposed s a l i n e - In f a c t one of Best's c o n t r o l groups, which was preexposed with s a l i n e ( t w ice), then given s a f e S a c c h a r i n f o l l o w e d by access to s a l i n e , showed an extremely s m a l l i n t a k e of s a l i n e - " 81 E3_PERIMENT V OVERSHADOWING'"IN~T&STE COMPOUNDS Pavlov (1927, p. 142) d i s c u s s e d the phenomenon of over-shadowing i n terms of the i n t e r a c t i o n s of d i f f e r e n t s t i m u l u s i n t e n s i t i e s . Overshadowing i s r e l a t e d t o the phenomenon known as " b l o c k i n g , " which has been e x t e n s i v e l y i n v e s t i g a t e d by Kamin (1968, 1969). The main d i f f e r e n c e between overshadowing and b l o c k i n g appears to c e n t e r on the past h i s t o r y of the animal. I f the animal has had s p e c i f i c c o n d i t i o n i n g to an element of a compound which subseguently i s shown to "overshadow" another independently c o n d i t i o n a b l e element, then one r e f e r s to t h i s as " b l o c k i n g " . However, i f t h i s p r i o r c o n d i t i o n i n g has not been demonstrated, then one c a l l s i t "overshadowing". Razran '(1965) r e l a t e s two Russian s t u d i e s concerned with the compounding of s t i m u l u s elements of d i f f e r i n g i n t e n s i t i e s . Z e l i o n y combined two sounds of d i f f e r i n g i n t e n s i t i e s , while Kash e r i n i n o v a combined two t a c t i l e CSs of d i f f e r i n g i n t e n s i t i e s i n a P a v l o v i a n s a l i v a r y c o n d i t i o n i n g procedure. They reported t h a t a f t e r t r a i n i n g to the compound, the weaker component f a i l e d t o e l i c i t a CR when presented s e p a r a t e l y even though capable of g a i n i n g c o n t r o l over behavior when used as the only CS. Kamin (1969) maintains t h a t overshadowing i s not p r i n c i p a l l y due t o the sensory masking of the weaker element by the s t r o n g e r element, but r a t h e r i s a f u n c t i o n of the d i f f e r e n t r a t e s of c o n d i t i o n i n g to weak and s t r o n g CSs. A s i m i l a r n o t i o n has been suggested by R e s c o r l a & Wagner (1972). Thus, asymptotic c o n d i t i o n i n g occurs more g u i c k l y to the s t r o n g CS r e l a t i v e to 82 the weak CS. The weaker CS becomes redundant to p r e d i c t i n g the occurrence of the UCS, and c o n d i t i o n i n g to i t s t o p s . The main support f o r t h i s c o n t e n t i o n are Kamin's experiments (1969). Kamin found t h a t a compound of l i g h t and tone f o l l o w e d by a 1 ma shock UCS r e s u l t e d i n c o n t r o l mainly by the l i g h t . However, when the UCS was i n c r e a s e d to 4 ma, overshadowing of the tone no l o n g e r o c c u r r e d . This procedure, i t was reasoned, enhanced the approach of both component CSs to t h e i r asymptotic c o n d i t i o n i n g l e v e l s , thus reducing d i f f e r e n c e s i n c o n d i t i o n a b i l i t y between d i f f e r e n t CSs. Kamin concluded, The f a c t t h a t l i g h t does not overshadow 50 db when an i n t e n s e US i s employed makes i t c l e a r t h at over-shadowing i s not a simple, d i r e c t , consequence of the r e l a t i v e i n t e n s i t i e s of c o n d i t i o n e d s t i m u l u s elements and seems t o e l i m i n a t e a simple a t t e n t i o n a l i n t e r p r e t a i o n of overshadowing (p.290). Experiment V was an attempt to i n v e s t i g a t e the phenomenon of overshadowing i n the c o n t e x t of simultaneous t a s t e s t i m u l u s compounds. R e l a t i v e s t r e n g t h s of the two s o l u t i o n s of a compound (NaCl and Saccharin) were manipulated. METHOD S ub -jects Each of f o u r groups of r a t s c o n s i s t e d of three male and t h r e e female f i r s t , second, and t h i r d g e n e r a t i o n Long-Evans-Agoutie c r o s s b r e e d s . 83 Procedure Table 6 shows the s o l u t i o n s presented to each group i n each major phase of the experiment. The procedure was s i m i l a r to that TABLE 6 Summary of procedure f o r each group showing t a s t e s o l u t i o n s presented i n each of the two major phases of Experiment V. Experimental phase Group C o n d i t i o n i n g ( S o l u t i o n - L i C l p a i r i n g ) E x t i n c t i o n (Test t r i a l s ) 1 NaCl+Saccharin NaCl+Saccharin NaCl S a c c h a r i n 2 N a C l - L i C l Saccharin (not paired) NaCl+Saccharin NaCl Saccharin 3 NaCl+Saccharin NaCl+Saccharin NaCl Saccharin f o r Groups 1 and 2 of Experiment IB, except t h a t a 0.35% S a c c h a r i n s o l u t i o n was s u b s t i t u t e d f o r the 0.25% S a c c h a r i n c o n c e n t r a t i o n . F o l l o w i n g b a s e l i n e water p r e s e n t a t i o n s , the Compound (1.0% NaCl+0.35% Saccharin) was presented to Group 1 s u b j e c t s f o r 10 min f o l l o w e d by an i n j e c t i o n of L i C l . On the f o l l o w i n g day, a l l s u b j e c t s were presented with 10 min access to water- The next day was the f i r s t t e s t day- Each s u b j e c t r e c e i v e d 10 min access to e i t h e r a Compound, NaCl or a Saccharin s o l u t i o n f o l l o wed by 10 min access to water. The seguence of s o l u t i o n p r e s e n t a t i o n over t h r e e day t e s t c y c l e s was counter-84 balanced as i n p r e v i o u s experiments u n t i l s e v e r a l measures f o r each f l u i d were obtained-Group 2 was used to show t h a t a 1.0% NaCl s o l u t i o n i s not overshadowed at the sensory l e v e l when i n compound with a 0.35% S a c c h a r i n s o l u t i o n . F o l l o w i n g s e v e r a l days of l i m i t e d access to water the s u b j e c t s were exposed t o a 0.35% S a c c h a r i n s o l u t i o n f o r t h r e e days f o r 10 min per day. F o l l o w i n g t h i s were th r e e more days of 10 min of water per day. On the s i x t h day a l l r a t s were given 10 min access to a 1.0% NaCl s o l u t i o n f o l l o w e d by L i C l i n j e c t i o n s . On the seventh day 10 min access t o Saccharin was g i v e n . NaCl was again presented on the e i g h t h day f o l l o w e d by L i C l i n j e c t i o n s . The t e s t i n g seguence began on the f o l l o w i n g day. Saccharin was presented f o r 10 min on the f i r s t two days of the t e s t i n g seguence. Ten min access to water always f o l l o w e d access to the t e s t s o l u t i o n s . On the t h i r d and f o u r t h day the c r i t i c a l t e s t was administered. The t e s t c o n s i s t e d of the p r e s e n t a t i o n of a compound s o l u t i o n c o n s i s t i n g of the " s a f e " 0.35% S a c c h a r i n s o l u t i o n and the a v e r s i v e 1.0% NaCl s o l u t i o n f o r 10 min to each animal. On the f i f t h t e s t day S a c c h a r i n was again presented f o l l o w e d by NaCl on the s i x t h t e s t day. The compound was again presented on the seventh, Saccharin on the e i g h t h and NaCl on the n i n t h and f i n a l t e s t day. Group 3 was administered the same procedure as Group 1. The s o l u t i o n s , however, were r e v e r s e d . The NaCl s o l u t i o n was now to serve as the s t r o n g e r (overshadowing) s o l u t i o n . The s t r e n g t h of S a c c h a r i n was reduced t o 0.15%. 85 Data P r e s e n t a t i o n and A n a l y s i s T h i s p a r t of the experiment was s i m i l a r to p r e v i o u s experiments. Repeated measure t - t e s t s were used only with o r t h o g o n a l pre- and p o s t - c o n d i t i o n i n g comparisons. A l l other comparisons used Tukey's HSD t e s t . RESULTS The r e s u l t s f o r Group 1 are presented i n F i g u r e 5-A. A c l e a r overshadowing e f f e c t was obtained. Every animal showed g r e a t e r i n t a k e of NaCl than S a c c h a r i n or Compound (g = 7.26). NaCl i n t a k e was 40% to 95$ g r e a t e r than S a c c h a r i n . S a c c h a r i n i n t a k e was a l s o reduced r e l a t i v e to c o n d i t i o n i n g day i n t a k e of the Compound (g = 5.15). Compound i n t a k e was s i m i l a r l y reduced i n every animal (g = 6.15). There were no d i f f e r e n c e s between i n t a k e of the Compound and S a c c h a r i n during e x t i n c t i o n . NaCl i n t a k e was not reduced r e l a t i v e t o i n t a k e of the Compound on the c o n d i t i o n i n g day. Intake of S a c c h a r i n and the Compound recovered to c o n d i t i o n i n g day l e v e l s of Compound i n t a k e by the second e x t i n c t i o n t r i a l . However, both were s t i l l reduced r e l a t i v e t o the i n t a k e of NaCl on the second t e s t t r i a l . By the t h i r d t r i a l i n t a k e l e v e l s of each s o l u t i o n were w i t h i n the range of b a s e l i n e water i n t a k e l e v e l s . The r e s u l t s f o r Group 2 r a t s are presented i n F i g u r e 5-B. I t i s obvious t h a t the presence of NaCl i n compound with S a c c h a r i n d r a s t i c a l l y reduced Sa c c h a r i n i n t a k e . T h i s e f f e c t was seen c l e a r l y i n every animal- NaCl consumption was reduced to a 86 I L_ I 1 1 I I B C 1 2 3 4 TRIALS f i g u r e 5-A. C o n d i t i o n i n g and e x t i n c t i o n f l u i d i n t a k e f o r Group 1. See F i g u r e 1-A f o r a b s c i s s a l a b e l i n g and e x p l a n a t i o n of symbols-low l e v e l r e l a t i v e to i t s c o n d i t i o n i n g day l e v e l f o l l o w i n g the f i r s t L i C l i n j e c t i o n - S accharin consumption on the f o l l o w i n g two days was with i n p r e i n j e c t i o n ranges. The r e s u l t s of the Compound t e s t confirm the d e t e c t a b i l i t y of 1.0% NaCl i n s o l u t i o n with 0.35% Saccharin- S a c c h a r i n consumption when i n compound with NaCl was reduced to a mean l e v e l of 0.95 ml on the f i r s t t e s t day and 2.27 ml on the second day compared to a mean Sac c h a r i n 87 ' ' i AV i C C 1 2 3 TRIALS F i g u r e 5-B. D i f f e r e n t i a l c o n d i t i o n i n g and e x t i n c t i o n f l u i d i n t a k e f o r Group 2- See F i g u r e 1-A f o r a b s c i s s a l a b e l i n g and an e x p l a n a t i o n of the symbols-i n t a k e of 13-83 ml on the p r e v i o u s day and 15.6ml on the day f o l l o w i n g the second Compound p r e s e n t a t i o n ( f i r s t Compound day vs f i r s t S a c c h a r i n t e s t day, t = 7.81). NaCl i n t a k e on the s i x t h t e s t day was suppressed i n a l l animals to 0.1 ml compared to an average i n t a k e of 23.92 ml on the f i r s t c o n d i t i o n i n g day (t = 33.75). Intake of the Compound was s t i l l reduced on the t h i r d p r e s e n t a t i o n r e l a t i v e to the t h i r d p o s t - c o n d i t i o n i n g S a c c h a r i n p r e s e n t a t i o n . 8 8 14 Q LU _> 310 CO z o o I B C 1 2 x TRIALS F i g u r e 5-C. C o n d i t i o n i n g and e x t i n c t i o n f l u i d i n t a k e f o r Group 3. See F i g u r e 1-A f o r a b s c i s s a l a b e l i n g and an e x p l a n a t i o n of t.he symbols. The r e s u l t s of Group 3 are shown i n F i g u r e 5-C. The r e s u l t s c o n t r a d i c t e d e x p e c t a t i o n s . Overshadowing d i d not occur. NaCl i n t a k e was not higher than S a c c h a r i n i n t a k e . Other r e s u l t s were i n accordance with p r e v i o u s experiments. Compound consumption d u r i n g the f i r s t t e s t seguence was reduced from c o n d i t i o n i n g day i n t a k e (g = 7.84). NaCl i n t a k e was reduced along with Saccharin (q = 4.77, 4.17; r e s p e c t i v e l y ) . E x t i n c t i o n of avoidance was e s s e n t i a l l y complete by the second t e s t f o r a l l s o l u t i o n s . 89 Summary. of R e s u l t s Overshadowing of a 1.0% NaCl s o l u t i o n by a 0.35% Saccharin s o l u t i o n o c c u r r e d , and was not due to an i n a b i l i t y of the r a t to d e t e c t the NaCl i n s o l u t i o n with S a c c h a r i n . The converse procedure of overshadowing S a c c h a r i n by NaCl was not s u c c e s s f u l . DISCUSSION The r e s u l t s of Group 1 s u b j e c t s c l e a r l y demonstrated overshadowing i n the g u s t a t o r y system of the r a t . The r e s u l t s of Group 2 demonstrate t h a t t h i s overshadowing was not due t o masking of the NaCl t a s t e . In f a c t the degree of su p p r e s s i o n of Compound consumption was somewhat s u r p r i s i n g . Apparently i t i s more adaptive i n t h i s s i t u a t i o n f o r the r a t t o overcompensate when presented with c o n f l i c t i n g s t i m u l i , one s i g n a l l i n g " s a f e " f o r consumption ( S a c c h a r i n ) , the other s i g n a l l i n g "unsafe" f o r consumption (NACL). I t i s as i f the r a t e r r s on the s i d e of prudence and uses the unsafe cue to a g r e a t e r degree than the s a f e cue i n determining f l u i d i n t a k e . T h i s i n t e r p r e t a t i o n would be c o n s i s t e n t with the r e s u l t s of Experiment IV. In t h a t experiment i n t a k e of the Compound was not a simple average of the i n t a k e of the sa f e and unsafe s o l u t i o n , but r a t h e r a weighted average f a v o r i n g the unsafe s o l u t i o n . Besides the c l e a r demonstration of overshadowing there i s another i n t e r e s t i n g aspect of the r e s u l t s of Group 1. I f one compares the r e s u l t s of Experiment I I I with the present r e s u l t s , the s i m i l a r i t y i s s t r i k i n g . In Experiment I I I NaCl was made " f a m i l i a r " , and then the Compound of NaCl+novel S a c c h a r i n was 90 f o l l o w e d by L i C l - T h i s r e s u l t e d i n the suppression of Saccharin i n t a k e accounting f o r most of the avoidance behavior- In the overshadowing experiment the c o n c e n t r a t i o n of S a c c h a r i n was i n c r e a s e d with s i m i l a r r e s u l t s - One c o u l d argue t h a t i n Experiment I I I avoidance behavior was d i r e c t e d to the novel s o l u t i o n because the f a m i l i a r one was a l e s s l i k e l y candidate (due to i t s never having been followed by s i c k n e s s i n the p a s t ) -In the present experiment avoidance behavior was d i r e c t e d t o the presumably more s a l i e n t (and more novel) cue. As Kamin (1968, 196 9) p r e v i o u s l y pointed out, however, s a l i e n c e per se i s c r i t i c a l only i n terms of approach t o asymptotic c o n d i t i o n i n g l e v e l of a CS. I t c o u l d be argued t h a t i n Experiment I I I S a c c h a r i n i n t a k e approached i t s asymptotic l e v e l more r a p i d l y than NaCl because of an enhanced s a l i e n c e or n o v e l t y due to the presence of the f a m i l i a r NaCl s o l u t i o n . S i m i l a r l y , the r e s u l t s of the present experiment could have occurred because the more s a l i e n t (and more novel) cue approached i t s asymptotic l e v e l of c o n d i t i o n i n g more r a p i d l y , thus r e s u l t i n g i n more suppression of S a c c h a r i n than NaCl i n t a k e -Sutherland & Mackintosh (1971) have accounted f o r overshadowing by p o s t u l a t i n g t h a t i f a compound s t i m u l u s (AB) i s presented to an animal, the animal w i l l a t t e n d (switch i n a n a l y z e r s ) to elements A and B i n r e l a t i o n to the s a l i e n c e of each s t i m u l u s . I f s t i m u l u s A i s h i g h l y s a l i e n t r e l a t i v e to s t i m u l u s B, c o n d i t i o n i n g w i l l occur to A and not to B. T h i s i s c a l l e d the " i n v e r s e h y p o t h e s i s , " i . e . , i n c r e a s e d a t t e n t i o n to one set of s t i m u l i n e c e s s a r i l y r e s u l t s i n a decrease i n a t t e n t i o n to some other s e t o f s t i m u l i - Overshadowing would 91 occur i n the present experiment ac c o r d i n g to t h i s a n a l y s i s because of the high s a l i e n c e of S a c c h a r i n r e l a t i v e t o the NaCl s o l u t i o n . E e s c o r l a & Wagner (1972) have f o r m a l i z e d another approach. They suggest t h a t each CS-UCS a s s o c i a t i o n grows at a c e r t a i n r a t e , and i f one CS i s more c o n d i t i o n a b l e than another, asymt o t i c c o n d i t i o n i n g t o the compound i s reached be f o r e the l e s s c o n d i t i o n a b l e CS i s f u l l y c o n d i t i o n e d . C o n d i t i o n i n g stops a t t h a t point to the l e s s c o n d i t i o n a b l e CS because the compound i s a l r e a d y f u l l y c o n d i t i o n e d . I t can then be s a i d t h a t any v a r i a b l e s which e i t h e r reduce or enhance the c o n d i t i o n a b i l i t y of one member of a compound CS w i l l show up i n the l e v e l of c o n d i t i o n i n g t o the other CS i n the compound. R e s c o r l a and wagner would e x p l a i n the overshadowing seen i n Group 1 by sugg e s t i n g t h a t i n c r e a s e d c o n c e n t r a t i o n of a s o l u t e enhances i t s approach to asymptotic c o n d i t i o n i n g l e v e l s , a c c o u n t i n g f o r most of the a s s o c i a t i v e s t r e n g t h of the compound. Mackintosh (1975b) has r e c e n t l y suggested a view somewhat s i m i l a r to E e s c o r l a & Wagner (1972) although d i f f e r i n g i n important d e t a i l s . Mackintosh b e l i e v e s that c o n d i t i o n i n g to the overshadowed s t i m u l u s stops because i t i s redundant to UCS p r e d i c t i o n , not because the compound i s f u l l y c o n d i t i o n e d (Mackintosh's f o r m u l a t i o n accounts f o r the " s u r p r i s e " e f f e c t seen i n rec e n t b l o c k i n g experiments; see d i s c u s s i o n of Experiment V I ) . Another more g e n e r a l f a c t o r r e l a t i n g t o the c o n d i t i o n i n g of a s t i m u l u s might be the concept of i n t e r f e r e n c e as p o s i t e d by 92 Revusky (1971). In accordance with t h i s view any s i t u a t i o n which reduces the number of p o s s i b l e CSs as p r e d i c t o r s of the DCS s h o u l d enhance c o n d i t i o n i n g of other p o t e n t i a l CSs. As p r e v i o u s l y noted S a c c h a r i n i n t a k e s uppression appeared to be g r e a t e r i n Experiment I I I than i n Experiment IB (Group 1). S i m i l a r l y , S a ccharin i n t a k e s u p p r e s s i o n i n Experiment V was 2.6 ml compared to 5.68 ml i n Experiment IB (Group 1). Although such between groups comparisons are not e n t i r e l y a p p r o p r i a t e , the r e s u l t s are again s u g g e s t i v e . I t would appear, as p r e v i o u s l y noted i n the d i s c u s s i o n of Experiment I I I , t h a t i f a p o t e n t i a l CS i s i n compound with a l e s s c o n d i t i o n a b l e CS (due e i t h e r to f a m i l i a r i t y or t o a s a l i e n c e f a c t o r ) i t s l e v e l of c o n d i t i o n i n g may be enhanced. Others have suggested that the degree to which a given cue c o n t r o l s behavior can depend a great deal on the other c o n t r o l l i n g cues present. The work of Maki and Death (1973) i l l u s t r a t e s t h i s p o s i t i o n . Although they d i d not i n v e s t i g a t e the a c g u i s i t i o n of element c o n t r o l i n a compound, but r a t h e r the use of the elements once stimulus c o n t r o l had been e s t a b l i s h e d , t h e i r work i s i n s t r u c t i v e . They used a matching-to-sample procedure with pigeons' key pecking as the response. A sample s t i m u l u s ( e i t h e r a l i n e , a c o l o r or a compound of both) was presented on the response key and then removed. F o l l o w i n g t h i s , two c h o i c e s t i m u l i , e i t h e r l i n e s or c o l o r s , appeared on the s i d e keys. Pecking the s t i m u l u s t h a t matched the p r e v i o u s l y presented sample st i m u l u s was r e i n f o r c e d . Performance was poorer when a compound sample was presented f o l l o w e d by elements as c h o i c e s t i m u l i than when elements were presented as samples f o l l o w e d by 9 3 elements. Maki and L e i t h concluded, The degree of c o n t r o l e x e r t e d by one element of a compound i s reduced when other elements present i n the compound a l s o c o n t r o l behavior (p. 349). Thus c o n t r o l by an element i s reduced when the pigeon must "share or d i v i d e i t s a t t e n t i o n " between the two cues. A l t e r n a t e l y they suggested i f one element of the compound i s not e x h i b i t i n g strong c o n t r o l with r e s p e c t to a c e r t a i n behavior, then the other element w i l l e x e r t c o r r e s p o n d i n g l y g r e a t e r c o n t r o l than otherwise p o s s i b l e . T h i s n o t i o n corresponds to the a n a l y s i s of the r e s u l t s o f Experiments IB (Group 1) and I I I (Group 1). In Experiment I I I avoidance behavior was under the c o n t r o l of Sa c c h a r i n to the e x c l u s i o n of NaCl because p r i o r f a m i l i a r i z a t i o n with NaCl had precluded i t as a s t r o n g source of c o n t r o l f o r avoidance behavior. In Experiment V S a c c h a r i n , presumably because of i t s enhanced c o n d i t i o n a b i l i t y , gained c o n t r o l over the avoidance behavior before NaCl, p r e v e n t i n g s u b s t a n t i a l c o n t r o l by NaCl from developing. In Experiment IB (Group 1) both elements c o n t r o l l e d avoidance behavior because both elements were p o s s i b l e sources of t o x i c o s i s . Thus, the r a t attended to both t a s t e s with the r e s u l t t h a t n e i t h e r t a s t e accounted f o r a l l of the avoidance behavior. T h i s i n t e r p r e t a t i o n can, of course, be extended t o the r e s u l t s of c o n d i t i o n i n g preexposed s t i m u l u s elements and t h e i r r e s p e c t i v e compounds (Experiment I A ) . The r e s u l t s of t h i s experiment suggest t h a t t h e r e i s an apparent asymmetry i n overshadowing with S a c c h a r i n and NaCl. Group 1 showed c l e a r overshadowing of NaCl by S a c c h a r i n . 94 However, f o r Group 3 overshadowing of Saccharin by NaCl was not obtained- T h i s may be due to the higher degree of n o v e l t y of S a c c h a r i n (thus i n c r e a s i n g i t s s u s c e p t i b i l i t y t o c o n d i t i o n i n g , K a l a t & Rozin, 1970; K a l a t , 1974) r e l a t i v e to NaCl, which, being present i n the r a t s ' l a b chow, may make i t l e s s n o v e l . A l s o , there i s the o f t e n noted b i o l o g i c a l mechanism o p e r a t i n g r e g a r d i n g sodium a p p e t i t e and i t s i n n a t e r e c o g n i t i o n (Krieckhaus, 1973). T h i s might c o n c e i v a b l y reduce the s u s c e p t i b i l i t y o f NaCl i n t a k e to suppression. However, as s e v e r a l experiments i n the present s e r i e s have demonstrated, NaCl i s h i g h l y c o n d i t i o n a b l e i n a t a s t e a v e r s i o n procedure-K a l a t 6 Rozin (1973), as w e l l as many other r e s e a r c h e r s , have demonstrated st r o n g a v e r s i o n s to a 1.0% NaCl s o l u t i o n . NaCl t a s t e a v e r s i o n s have a l s o p e r s i s t e d even when r a t s were adrenalectomized or i n j e c t e d with f o r m a l i n (Balagura, Brophy, S Davenport, 1972). Balagura e t al j _ s . r e s u l t s c l e a r l y showed that the b i o l o g i c a l mechanism of sodium a p p e t i t e can be ov e r r i d d e n i f enough N a C l - L i C l p a i r i n g s occur. This i s c o n t r a r y t o Frumkin (1971), who concluded on the b a s i s of N a C l - L i C l p o i s o n i n g t h a t the s a l t - s e e k i n g behavior of sodium-depleted r a t s i s b a s i c a l l y " u n m o d i f i a b l e " . However, i t should be pointed out that a sodium need-state does r e s u l t i n guicker recovery of NaCl consumption (Balagura & Smith, 1970). The p o s s i b i l i t y o f an i n n a t e sodium a p p e t i t e accounting f o r the d i f f i c u l t y of g e t t i n g overshadowing i s tenuous at b e s t . A more parsimonious e x p l a n a t i o n would be the reduced n o v e l t y of NaCl because of i t s presence i n the r a t chow or c o n v e r s e l y because of the high s a l i e n c e or n o v e l t y of S a c c h a r i n . 95 Revusky (1971) using s e q u e n t i a l p r e s e n t a t i o n s of a Vinegar and S a c c h a r i n s o l u t i o n , r e p o r t e d d i f f i c u l t y i n overshadowing a 0.1% S a c c h a r i n s o l u t i o n with a Vinegar s o l u t i o n as high as 4.5%. I t i s i n t e r e s t i n g to note that Revusky i n another experiment almost completely overshadowed a 1.25% Coffee or a 3.0% Vinegar s o l u t i o n by a 2.0% Saccharin s o l u t i o n presented f o r 15 min f o l l o w e d by immediate access to 5 ml of C o f f e e or Vinegar s o l u t i o n . T o x i c o s i s f o l l o w e d one hour l a t e r . Eevusky's use of a 2.0% Saccharin s o l u t i o n i s i n s t r u c t i v e . T h i s c o n c e n t r a t i o n i s e i g h t times t h a t used i n most of the experiments of t h i s s e r i e s (0.25%). G a r c i a et a l . (1974) on l y r e p o r t e d data on c o n d i t i o n e d a v e r s i o n s using up to a 0.7% S a c c h a r i n s o l u t i o n . I f appears t h a t overshadowing of c e r t a i n t a s t e s t i m u l i may be d i f f i c u l t i n some circumstances. Of course t h i s asymmetry of overshadowing e f f e c t s i s not unique to the g u s t a t o r y system- Baron (1965) has argued f o r the p r e d i s p o s i t i o n i n pigeons to attend to c o l o r over form. Thus, t h e i r responding u s u a l l y comes under the c o n t r o l of the c o l o r element of a compound s t i m u l u s composed of a white l i n e on a c o l o r e d background (see a l s o Johnson & Cumming, 1968). Mention should be made r e g a r d i n g the overshadowing of S a c c h a r i n by NaCl i n Experiment 1A (Group 1, Figure 1-A). A l l s i x r a t s showed a g r e a t e r consumption of S a c c h a r i n than NaCl d u r i n g the f i r s t , second, and t h i r d t e s t . I t would appear t h a t preexposure of NaCl and S a c c h a r i n r e s u l t e d i n g r e a t e r " l e a r n e d s a f e t y " or " i r r e l e v a n c e " (Kalat & Rozin, 1973) f o r Saccharin than NaCl. According to E e s c o r l a S Wagner (1972) a s t i m u l u s f a c t o r (e.<j., s a l i e n c e ) c o n t r i b u t e s to amount of c o n d i t i o n i n g i n a p a r t i c u l a r s i t u a t i o n . I f t h i s f a c t o r i s high then g r e a t e r 96 asymptotic c o n d i t i o n i n g w i l l occur- As we have already seen (Experiment V) novel Saccharin appears to be more c o n d i t i o n a b l e than novel. NaCl- Thus, one would p r e d i c t that S a c c h a r i n when preexposed would show a g r e a t e r asymptotic " s a f e " c o n d i t i o n i n g l e v e l than NaCl- I f t h i s i s t r u e then one would p r e d i c t t h a t NaCl would subsequently overshadow Sa c c h a r i n when both are put i n compound and f o l l o w e d by t o x i c o s i s - T h i s i s i n f a c t e x a c t l y what occurred- Group 2 s u b j e c t s d i d not show overshadowing of Sa c c h a r i n by NaCl, presumably because of t h e i r p r i o r S a c c h a r i n -L i C l c o n d i t i o n i n g . 97 JXPEEIMENT VI BLOCKING,: CONDITIONING TO THE _ELEMENTS OF A COMPOUND 2ASTE STIMULUS AFTER PRIOR CONDITIONING TO ONE ELEMENT Kamin (1968, 1969) d i d the f i r s t s y s t e m a t i c work on the " b l o c k i n g " e f f e c t . The b a s i c procedure i n v o l v e d f i r s t t r a i n i n g an animal t o respond d i f f e r e n t i a l l y t o two stim u l u s c o n d i t i o n s (which may j u s t be the presence or absence of a s t i m u l u s ) . F o l l o w i n g some c r i t e r i o n of d i s c r i m i n a t i o n performance, another set of cues are added to the e a r l i e r s e t , forming a compound. These e x t r a cues are n e c e s s a r i l y redundant. C o n t r o l of an animal's responding by the added redundant element, even a f t e r prolonged t r a i n i n g with the compound, i s u s u a l l y l e s s than i n animals t r a i n e d only with the compound. Kamin's work, done with r a t s and a c o n d i t i o n e d s u p p r e s s i o n paradigm, has proven t o be a ro b u s t and dependable b e h a v i o r a l phenomenon. Others (Johnson & Cumming, 1968; M i l e s & J e n k i n s , 1965; W i l l i a m s , 1975) have demonstrated the e f f e c t with pigeons i n an a p p e t i t i v e s i t u a t i o n . B l o c k i n g has a l s o been demonstrated i n g o l d f i s h and carp (Tennant & Bitterman, 1975). Two d i f f e r e n t r e s e a r c h e f f o r t s (Revusky, 1971; K a l a t & Rozin, 1972) have attempted to demonstrate the b l o c k i n g e f f e c t using the t a s t e a v e r s i o n procedure. Revusky c l a i m s that b l o c k i n g can be obta i n e d , while K a l a t and Rozin argue that b l o c k i n g does not occur. The experiments d i f f e r i n s e v e r a l ways. One obvious d i f f e r e n c e i s t h a t Revusky f o l l o w e d h i s f i r s t c o n d i t i o n e d s o l u t i o n with t o x i c o s i s on two o c c a s i o n s before p a i r i n g i t i n a s u c c e s s i v e f a s h i o n with another s o l u t i o n and f o l l o w i n g t h i s " s e q u e n t i a l " ompound with i l l n e s s . K a l a t and Rozin i n j e c t e d 98 t h e i r animals once f o l l o w i n g i n t a k e of the f i r s t s o l u t i o n before p a i r i n g i t with the second s o l u t i o n and f o l l o w i n g both by s i c k n e s s . Revusky's procedure should f a v o r a b l o c k i n g e f f e c t . As Kamin suggested, i f c o n d i t i o n i n g i s a l r e a d y w e l l advanced t o the f i r s t cue, then c o n d i t i o n i n g to the added cue w i l l be r e t a r d e d . Experiment VI was done to e l a b o r a t e the b l o c k i n g phenomenon as i t r e l a t e s to the g u s t a t o r y - m a l a i s e system of the r a t . The major d i f f e r e n c e s between the present s e r i e s of experiments and the experiments of Revusky, Kalat and Rozin a r e : f i r s t , the present experiments u t i l i z e p r i m a r i l y a w i t h i n s u b j e c t s procedure. Second, the separate s o l u t i o n s are mixed together to form a compound s o l u t i o n . Simultaneous p r e s e n t a t i o n of the elements i s the usual procedure f o r i n v e s t i g a t i n g compound st i m u l u s c o n t r o l . Both Revusky, and K a l a t and Rozin presented the elements of the compound s t i m u l i s e r i a l l y , i . e . , s o l u t i o n A then s o l u t i o n B, then s i c k n e s s . The procedures f o r the f i r s t two groups were attempts to o b t a i n b l o c k i n g . The t h i r d group was e s s e n t i a l l y a r e p l i c a t i o n of Experiment IB where a compound of two novel f l a v o r s was f o l l o w e d by i l l n e s s . T h i s was done so t h a t a comparison could be made between t a s t e element s u p p r e s s i o n i n a b l o c k i n g and non-b l o c k i n g procedure. Group 4 was exposed t o a procedure s i m i l a r t o the procedure cf Group 1 except that the t a s t e s o l u t i o n s used were preexposed. Group 5 r e c e i v e d s i m i l a r procedures except t h a t the t a s t e s o l u t i o n f i r s t c o n d i t i o n e d was p a i r e d with t o x i c o s i s s e v e r a l times beyond the number necessary f o r 100% suppression ( i . e . , these r a t s were o v e r t r a i n e d with the f i r s t t a s t e ) . Group 99 6 r e c e i v e d the b a s i c b l o c k i n g procedure except the L i C l doses were reduced t o approximately 1/8 of the usual dose f o r the pre-as well as the post-compounding c o n d i t i o n i n g phase. T h i s , of c o u r s e , n e c e s s i t a t e d s e v e r a l i n j e c t i o n s both p r i o r to and f o l l o w i n g the compounding of the a v e r s i v e t a s t e element with the added t a s t e element. Group 7 r e c e i v e d e x t e n s i v e preexposure to the to-be-added s o l u t i o n . Then f o l l o w i n g c o n d i t i o n i n g to the added s o l u t i o n both preexposed and b l o c k i n g s o l u t i o n s were compounded and f o l l o w e d by L i C l f i v e times- Groups 4-7 were i n t r o d u c e d when b l o c k i n g was not obtained with Groups 1 or 2. The procedure f o r groups 4-7 was designed to o b t a i n l e s s c o n d i t i o n i n g to the added t a s t e element by various manipulations such as reducing the c o n d i t i o n a b i l i t y of the added s t i m u l u s (Groups 4,6, & 7 ) , or by i n c r e a s i n g the l e v e l of c o n d i t i o n i n g of the f i r s t s t i m u l u s (Group 5) to a point where l i t t l e c o n d i t i o n i n g to the added s t i m u l u s should o c c u r . METHOD Sub j e c t s Seven groups of r a t s , 3 male and 3 female f i r s t , second, and t h i r d g e n e r a t i o n c r ossbreeds per group, served as s u b j e c t s . Procedure Table 7 shows the t a s t e s o l u t i o n s used i n each major phase of the experiment. A l l Group 1 s u b j e c t s r e c e i v e d b a s e l i n e access t o 10 min water per day f o r s e v e r a l days. On the f o l l o w i n g day a l l s u b j e c t s were presented with 10 min access to the f i r s t 100 t a s t e s t i m u l u s , a 0,25% Saccharin s o l u t i o n - Within 10 min of the t e r m i n a t i o n of access to Saccharin a l l r a t s were i n j e c t e d with the standard L i C l dose. On the day f o l l o w i n g a l l s u b j e c t s were given 10 min access t o water. On the next day a l l s u b j e c t s r e c e i v e d 10 min access to a Compound s o l u t i o n of 1.0% NaCl and 0.25% S a c c h a r i n . T h i s p r e s e n t a t i o n was f o l l o w e d within 10 min by a standard i n j e c t i o n of L i C l . On the f o l l o w i n g day 10 min access t o water was given. Over the next t h r e e days the t e s t c y c l e of Compound, NaCl, and Saccharin o c c u r r e d . The s o l u t i o n s were presented, one each day, counterbalanced over a l l r a t s , f o r 10 min per day f o l l o w e d by TO min access t o water. T h i s c y c l e was repeated s e v e r a l times. Group 2 s u b j e c t s were t r e a t e d i n an i d e n t i c a l manner except t h a t NaCl was the f i r s t s t i m u l u s p a i r e d with L i C l r a t h e r than S a c c h a r i n . NaCl was then compounded with S a c c h a r i n and followed with L i C l , Group 3 was a c o n t r o l f o r Groups 1 and 2. For these s u b j e c t s t h e r e was no p r e c o n d i t i o n i n g phase ( p r i o r NaCl or S a c c h a r i n p a i r i n g with L i C l ) . F o l l o w i n g s e v e r a l b a s e l i n e days with water the Compound of S a c c h a r i n plus NaCl was f o l l o w e d by t o x i c o s i s once (as i n Experiment IB). Access to the Compound was l i m i t e d t o approximately 2 rain i n order to keep amount consumed approximately e q u a l t o t h a t of Groups 1 and 2. F o l l o w i n g a day with water alone t e s t t r i a l s began. Group 4 r e c e i v e d one preexposure t o both NaCl and Saccharin b e f o r e the c o n d i t i o n i n g phase began. F o l l o w i n g t h i s preexposure S a c c h a r i n was p a i r e d with L i C l twice, then put i n compound with TABLE 7 101 Summary of procedure f o r each group, showing t a s t e s o l u t i o n s presented i n each of the three major phases of Experiment VI-Experimental phase F i r s t c o n d i - Second c o n d i -t i o n i n g phase t i o n i n g phase ( S o l u t i o n - L i C l ( S o l u t i o n - L i C l E x t i n c t i o n Group Preexposure p a i r i n g ) p a i r i n g ) T e s t - t r i a l s S a c charin Saccharin + NaCl Saccharin + NaCl NaCl Saccharin NaCl Sa c c h a r i n + NaCl Saccharin + NaCl NaCl Saccharin S a c c h a r i n + NaCl Saccharin + NaCl NaCl Saccharin S a c c h a r i n NaCl Saccharin Saccharin S a c c h a r i n S a c c h a r i n + NaCl Saccharin + NaCl Saccharin + NaCl Saccharin + NaCl NaCl Sa c c h a r i n Saccharin + NaCl NaCl Saccharin Vinegar Saccharin + NaCl Saccharin NaCl NaCl (1/2 group) Sa c c h a r i n (1/2 group) Saccharin (1/2 group ) NaCl (1/2 group) S a c c h a r i n + N a c i Saccharin + NaCl Saccharin NaCl Vinegar 102 NaCl and followed once by L i C l . T e s t i n g was c a r r i e d out as i n pre v i o u s groups-Group 5 was e s s e n t i a l l y a r e p l i c a t i o n of Group 1 except t h a t S a c c h a r i n was p a i r e d three times with L i C l i n s t e a d o f only once. Because i n t a k e of Saccharin on i t s t h i r d c o n d i t i o n i n g day was expected t o be very l i m i t e d , 5 ml of Sac c h a r i n was i n j e c t e d d i r e c t l y i n t o the mouth of each r a t on the t h i r d S a c c h a r i n - L i C l day. T h i s procedure was a l s o f o l l o w e d on the Compound-LiCl day. Besides NaCl, S a c c h a r i n , and the Compound being presented d u r i n g t e s t i n g , a 2-5% Vinegar s o l u t i o n was a l s o presented to assess any g e n e r a l neophobic r e a c t i o n s . Group 6 was t r e a t e d s i m i l a r l y t o Group 1 except t h a t the i n i t i a l L i C l dose was reduced from 2.0% to 0.25% of body weight (a r e d u c t i o n t o 1/8 the o r i g i n a l L i C l dose). Because of the l a c k of c o n d i t i o n i n g to the f i r s t t a s t e (Saccharin) i n t h r e e female r a t s , the dose of L i C l f o r these s u b j e c t s was i n c r e a s e d to 0.5% of body weight. Group 7 was d i v i d e d i n t o two subgroups of t h r e e r a t s each. One subgroup was preexposed to NaCl f o r 20 days. The other subgroup was preexposed t o S a c c h a r i n f o r 20 days. F o l l o w i n g t h i s the NaCl preexposed r a t s r e c e i v e d one S a c c h a r i n - L i C l p a i r i n g , while the Saccharin preexposed r a t s r e c e i v e d one N a C l - L i C l p a i r i n g - A day with water i n t e r v e n e d , and then both subgroups r e c e i v e d f i v e Compound ( N a C l + S a c c h a r i n ) - L i C l p a i r i n g s with water i n t e r s p e r s e d between c o n d i t i o n i n g days. F o l l o w i n g the c o n d i t i o n i n g sequence the normal t e s t i n g procedure began, except t h a t a novel 2.5% Vinegar s o l u t i o n was presented during the 103 f i r s t t e s t c y c l e . Data P r e s e n t a t i o n and a n a l y s i s T h i s aspect of the experiment was s i m i l a r to the a n a l y s i s performed i n previous experiments except that between groups t t e s t s with n1+n2-2 degrees of freedom were a l s o used. RESULTS The r e s u l t s f o r Groups 1 and 2 are shown i n F i g u r e s 6- A and 6-B. B l o c k i n g was not evidenced i n e i t h e r Groups 1 or 2. S u b j e c t s i n both groups showed l i t t l e i n t a k e of the t a s t e s o l u t i o n added a f t e r p r e c o n d i t i o n i n g . Figure 6-A shows the r e s u l t s f o r Group 1. F o l l o w i n g one S a c c h a r i n - L i C l p a i r i n g consumption of the Saccharin+NaCl Compound was at a low l e v e l r e l a t i v e to c o n d i t i o n i n g day S a c c h a r i n l e v e l s (g = 15-58). The e x t i n c t i o n t e s t s f o l l o w i n g one Compound-LiCl p a i r i n g showed no evidence of any a p p r e c i a b l e consumption of NaCl (added s o l u t i o n ) . Intake o f NaCl remained reduced from the f i r s t S a c c h a r i n - L i C l c o n d i t i o n i n g day f o r two t e s t p r e s e n t a t i o n s ( f i r s t day, g = 15.48). Saccharin i n t a k e remained reduced from i t s i n i t i a l c o n d i t i o n i n g day i n t a k e f o r f o u r t e s t p r e s e n t a t i o n s ( f i r s t day, g = 15.24). Intake of the Compound remained reduced r e l a t i v e t o i n i t i a l S a c c h a r i n i n t a k e f o r the d u r a t i o n of the t e s t i n g seguence. Compound i n t a k e never d i f f e r e d from Sa c c h a r i n i n t a k e d u r i n g the e x t i n c t i o n t e s t s . Compound i n t a k e d i f f e r e d from NaCl i n t a k e a f t e r the t h i r d t e s t . B a s i c a l l y the same t h i n g occurred between 104 14 Q UJ 310 CO z o o 6 • 6 B C C 1 2 3 4 5 TRIALS F i g u r e 6-A, C o n d i t i o n i n g and e x t i n c t i o n f l u i d i n t a k e f o r Group 1. See Fi g u r e 1-A f o r a b s c i s s a l a b e l i n g and an e x p l a n a t i o n of the symbols. S a c c h a r i n and NaCl i n t a k e . Group 2 r e s u l t s are shown i n F i g u r e 6-B. Again the added s o l u t i o n was avoided (consumption ranged between 0.1 and 3 ml), S a c c h a r i n i n t a k e remained lower than i n i t i a l c o n d i t i o n i n g day i n t a k e of NaCl f o r the d u r a t i o n of the e x t i n c t i o n t e s t . Intake of NaCl remained reduced from i t s i n i t i a l c o n d i t i o n i n g day i n t a k e u n t i l the f o u r t h e x t i n c t i o n p r e s e n t a t i o n . During each 105 t e s t there were no d i f f e r e n c e s between i n t a k e s of the d i f f e r e n t s o l u t i o n s -C C 1 2 TRIALS F i g u r e 6-B. C o n d i t i o n i n g and e x t i n c t i o n f l u i d i n t a k e f o r Group 2. See F i g u r e 1-A f o r an e x p l a n a t i o n of a b s c i s s a l a b e l i n g and the symbols. F i g u r e 6-C shows the r e s u l t s f o r Group 3. Note the degree o f s i m i l a r i t y between t h i s f i g u r e and F i g u r e 1-E (panel 1), Experiment IB. Of main i n t e r e s t r e g a r d i n g Group 3 r a t s i s t h e i r 106 i n t a k e of NaCl and Saccharin compared t o Group 1 and 2 r a t s -Comparing the i n t a k e of NaCl f o r Group 3 with t h a t of Group 1 {NaCl was the added s o l u t i o n ) shows t h a t Group 3 consumed more than Group 1 (t = 3.0)- This d i f f e r e n c e p e r s i s t s d u r i n g the second (t = 5.17) and t h i r d t e s t t r i a l (t = 3.15). Group 2 showed s i m i l a r r e s u l t s . Mean Sac c h a r i n i n t a k e f o r the f i r s t t e s t p r e s e n t a t i o n f o r Group 3 was higher than the intake of Group 2 (in which Sa c c h a r i n was the added s o l u t i o n , t = 2-63). Saccharin i n t a k e f o r the second t e s t t r i a l d i d not d i f f e r between groups. The other r e s u l t s f o r Group 3 were i n c l o s e correspondance to those d e s c r i b e d i n p r i v i o u s experiments of a s i m i l a r nature (e. £. , Experiment I B ) . Group 4 r a t s ' i n t a k e of the added s o l u t i o n (NaCl) was h i g h e r than the i n t a k e of the f i r s t ( s o l u t i o n ) as shown i n F i g u r e 6-D (g = 4.44). NaCl i n t a k e d u r i n g the second and subseguent t e s t s was s i g n i f i c a n t l y g r e a t e r than S a c c h a r i n i n t a k e . NaCl i n t a k e was g r e a t e r than i n t a k e of the Compound f o r a l l t e s t t r i a l s . The remaining comparisons confirmed p r e v i o u s r e s u l t s . The r e s u l t s f o r Group 5 are presented in F i g u r e 6-E. I t i s r e a d i l y apparent t h a t i n t a k e of the added s o l u t i o n (NaCl) was reduced i n amounts comparable t o Saccharin and the Compound of NaCl+Saccharin. NaCl i n t a k e compared to p r e c o n d i t i o n i n g i n t a k e of S a c c h a r i n was reduced during the f i r s t (g = 12.2 8) and second t e s t s . By the f o u r t h t e s t NaCl i n t a k e f a r exceeded p r e c o n d i t i o n i n g S a c c h a r i n i n t a k e i n a l l animals but one. F u r t h e r c o n f i r m a t i o n of the reduced i n t a k e of NaCl comes from comparing 107 B C 1 2 3 4 5 ; TRIALS F i g u r e 6-C. C o n d i t i o n i n g and e x t i n c t i o n f l u i d i n t a k e f o r Group 3- See F i g u r e 1-A f o r a b s c i s s a l a b e l i n g and an e x p l a n a t i o n of the - symbols. NaCl with Saccharin and Compound i n t a k e s d u r i n g the f i r s t t e s t . As Figure 6-E c l e a r l y shows, i n t a k e was almost zero i n a l l animals. Thus, although NaCl i n t a k e recovered f a s t e r , as has o f t e n o c c u r r e d , i t s i n t a k e was reduced i n i t i a l l y t o l e v e l s comparable to t h a t of the other t a s t e s o l u t i o n s d e s p i t e complete c o n d i t i o n i n g t o the S a c c h a r i n s o l u t i o n p r i o r to Compound-LiCl p a i r i n g . 108 IT TRIALS F i g u r e 6-D. Preexposure, c o n d i t i o n i n g , and e x t i n c t i o n f l u i d i n t a k e f o r Group 4. See F i g u r e 1-A f o r an e x p l a n a t i o n of a b s c i s s a l a b e l i n g and symbols-Intake of Vinegar, the c o n t r o l f o r neophobia, did not d i f f e r compared to p r e c o n d i t i o n i n g S a c c h a r i n i n t a k e during e i t h e r the f i r s t or second t e s t s . Vinegar i n t a k e was g r e a t e r than NaCl i n t a k e during the f i r s t t e s t (g = 10.89). This d i f f e r e n c e was s t i l l l a r g e during the second t e s t t r i a l . Other r e s u l t s were comparable to p r e v i o u s experiments. S a c c h a r i n i n t a k e dropped d r a m a t i c a l l y f o l l o w i n g the f i r s t L i C l 1 0 9 A B C C C C 1 2 3 4 5 TRIALS F i g u r e 6-E. C o n d i t i o n i n g and e x t i n c t i o n f l u i d i n t a k e f o r Group 5- See F i g u r e 1-A f o r a b s c i s s a l a b e l i n g and an e x p l a n a t i o n of the symbols-i n j e c t i o n and remained extremely low f o r the f i v e post-c o n d i t i o n i n g e x t i n c t i o n t e s t seguences. Intake of the Compound a l s o remained reduced f o r the d u r a t i o n of t e s t i n g . Intake o f S a c c h a r i n and the Compound never d i f f e r e d a p p r e c i a b l y d u r i n g t e s t i n g . Both i n t a k e of Saccharin and o f the Compound were reduced compared to Vinegar i n t a k e during the f i r s t and second t e s t s (g = 10.94, 10. 98; r e s p e c t i v e l y ) . 110 F i g u r e 6-F shows the r e s u l t s of Group 6. Because of the slow c o n d i t i o n i n g i n the females, which n e c e s s i t a t e d extended c o n d i t i o n i n g t r i a l s , only the f i r s t S a c c h a r i n - L i C l p a i r i n g i s shown. The data of main i n t e r e s t are the r e d u c t i o n i n i n t a k e of the added s o l u t i o n , NaCl. I t i s r e a d i l y apparent t h a t NaCl i n t a k e was low (4.0 ml). However, t h i s d i f f e r e n c e was not s i g n i f i c a n t when compared to the f i r s t S a c c h a r i n - L i C l c o n d i t i o n i n g day. The reason f o r t h i s i s t h a t f o u r r a t s (three males and one female) showed NaCl i n t a k e s o f 0.1 ml to 1.0 ml while two female r a t s showed i n t a k e s of 13 ml and 10 ml. Thus, one c o u l d argue f o r a b l o c k i n g e f f e c t i n these two females, but c e r t a i n l y no b l o c k i n g occurred i n the remaining s u b j e c t s . During the f i r s t t e s t t r i a l NaCl i n t a k e d i d not d i f f e r from Compound i n t a k e or Saccharin i n t a k e . NaCl i n t a k e was, however, s i g n i f i c a n t l y lower than Vinegar i n t a k e . NaCl i n t a k e continued to i n c r e a s e as i t d i d i n Group 1. NaCl i n t a k e as compared to Compound or Saccharin i n t a k e remained unchanged during the second t e s t t r i a l , began to d i v e r g e on the t h i r d t e s t t r i a l , and by the f o u r t h t e s t t r i a l was c l e a r l y g r e a t e r than Compound or Saccharin i n t a k e i n every animal. Other r e s u l t s were s i m i l a r t o t h a t of previous experiments. Intake of a l l s o l u t i o n g r a d u a l l y i n c r e a s e d over e x t i n c t i o n t r i a l s . I t i s important to note t h a t i n t a k e of Vinegar, the n o v e l -unpaired t a s t e s o l u t i o n , remained r e l a t i v e l y high as i t d i d i n Group 5 r a t s . Average i n t a k e of Vinegar was 11.8 ml d u r i n g the f i r s t t e s t , which was c o n s i d e r a b l y higher than i n t a k e of any of 111 B C 1 2 3 4 5 i TRIALS F i g u r e 6-F. C o n d i t i o n i n g and e x t i n c t i o n f l u i d i n t a k e f o r Group 6- See Fig u r e 1-A f o r a b s c i s s a l a b e l i n g and an e x p l a n a t i o n of the symbols. the other s o l u t i o n s . The data f o r both subgroups of Group 7 s e r e combined t o f a c i l i t a t e p r e s e n t a t i o n . Figure 6-G c l e a r l y shows t h a t f o l l o w i n g f i v e Compound-LiCl p a i r i n g s the s o l u t i o n t h a t was subseguently added to the Compound as the second s o l u t i o n was avoided t o an e x t e n s i v e degree by a l l r a t s . A l s o note the l a c k of any 112 s u b s t a n t i a l i n t a k e s u p p r e s s i o n to the novel Vinegar s o l u t i o n -14 Q UJ 310 CO o o _ l ^ 6 B C C 5 1 2 i. TRIALS F i g u r e 6-G. Preexposure, c o n d i t i o n i n g , and e x t i n c t i o n f l u i d i n t a k e f o r Group 7. See Fig u r e 1-A f o r a b s c i s s a l a b e l i n g . F i l l e d symbols correspond to water ( ) . preexposed s o l u t i o n subseguently added to Compound ( ^ ^ ) , f i r s t c o n d i t i o n e d s o l u t i o n a n ^ Compound ( £ ) . U n f i l l e d symbols show water i n t a k e f o r c o r r e s p o n d i n g f i l l e d symbols. 113 Summary, of R e s u l t s I t i s c l e a r t h a t c o n d i t i o n i n g to a novel or f a m i l i a r t a s t e o ccurs even when i n compound with an a l r e a d y s t r o n g l y c o n t i f i o n e d CS- Intake s u p p r e s s i o n to the added s t i m u l u s i s s i m i l a r to s u p p r e s s i o n obtained when the s t i m u l u s alone i s p a i r e d with L i C l - Intake of a novel unpaired s o l u t i o n i s not g r e a t l y reduced compared to the compound and the elements. DISCUSSION Evidence f o r b l o c k i n g i n t a s t e a v e r s i o n l e a r n i n g would occur i f a novel s o l u t i o n , put i n compound with an a l r e a d y e s t a b l i s h e d a v e r s i v e s o l u t i o n and f o l l o w e d by t o x i c o s i s , was rendered l e s s a v e r s i v e than when put i n compound with a novel s o l u t i o n (no p r i o r c o n d i t i o n i n g ) and f o l l o w e d by t o x i c o s i s . The r e s u l t s of Groups 1 and 2 d i d not show such a b l o c k i n g e f f e c t . However, i t i s obvious t h a t avoidance o f the added s o l u t i o n , NaCl, i n Group 1 e x t i n g u i s h e d much f a s t e r than avoidance of e i t h e r Saccharin or the Compound- Revusky's (1971) data showed b l o c k i n g on the i n i t i a l e x t i n c t i o n t e s t t r i a l as w e l l as more r a p i d e x t i n c t i o n over t e s t t r i a l s - The r e s u l t s of Group 2, however, showed that avoidance of S a c c h a r i n (the added s o l u t i o n ) d i d not show the r a p i d e x t i n c t i o n c h a r a c t e r i s t i c of NaCl avoidance- I t thus appears t h a t the r a p i d e x t i n c t i o n of NaCl avoidance i n Group 1 was not due to any b l o c k i n g e f f e c t , but r a t h e r to the choice of s o l u t i o n s . I f , a c c o rding to Kamin (1969) as w e l l as R e s c o r l a and Wagner (1972), c o n d i t i o n i n g i s well advanced when a redundant 114 s t i m u l u s i s put i n compound, then l i t t l e c o n d i t i o n i n g should occur to the added redundant s t i m u l u s . Previous experiments have shown that a s i n g l e s o l u t i o n - L i C l p a i r i n g r e s u l t s i n s u b s t a n t i a l avoidance of the p a i r e d ' s o l u t i o n - Avoidance o f the added s o l u t i o n should at l e a s t be c o n d i t i o n e d t o a l e s s e r degree than when the s i n g l e s t i m u l u s i s simply f o l l o w e d by t o x i c o s i s . S u p r i s i n g l y , i f one compares the r e s u l t s of Groups 1 and 2 with Group 3 p r i o r c o n d i t i o n i n g with one t a s t e a c t u a l l y appeared to r e s u l t i n g r e a t e r avoidance of the redundant t a s t e subsequently added to the Compound. Further support f o r s u b s t a n t i a l c o n d i t i o n i n g of the added element comes from a comparison of Compound and element i n t a k e s . Intake of the added s o l u t i o n s d i d not d i f f e r from i n t a k e of the Compound i n Groups 1 and 2, while, i n Experiments 1A and 1B there was g e n e r a l l y a s u b s t a n t i a l d i f f e r e n c e between i n t a k e of the Compound and i t s r e s p e c t i v e t a s t e elements. Kamin (1969) as well as Mackintosh (1975) has i n d i c a t e d t h a t something i s l e a r n e d about the added s t i m u l u s at l e a s t upon i t s f i r s t p r e s e n t a t i o n i n compound. As Experiments IA and IB showed, i f a compound t a s t e i s f o l l o w e d by t o x i c o s i s c o n s i d e r a b l e c o n d i t i o n i n g occurs to the t a s t e elements. T h e r e f o r e , i f the animal j u s t shows a normal increment of c o n d i t i o n i n g on t h i s one compound t r i a l , some avoidance of the added t a s t e should be apparent. In f a c t the degree of s u p p r e s s i o n of the added s o l u t i o n (NaCl or Saccharin) of Groups 1 and 2 was comparable to when only a s i n g l e s o l u t i o n was f o l l o w e d by t o x i c o s i s (Experiment I I ) . T h i s i s confirmed by a comparison of the suppression of the added t a s t e s o l u t i o n s i n 115 Groups 1 and 2 with the s uppression of these same s o l u t i o n s i n Group 3 where no p r i o r c o n d i t i o n i n g was a d m i n i s t e r e d . In both cases there was a g r e a t e r r e d u c t i o n i n i n t a k e of the t a s t e element than when only the Compound was f o l l o w e d by t o x i c o s i s with no p r i o r c o n d i t i o n i n g t o one other t a s t e element. I t appears t h a t the presence of a t a s t e element made a v e r s i v e by c o n d i t i o n i n g allows complete c o n d i t i o n i n g of avoidance of the added t a s t e . One p o s s i b i l i t y i n accounting f o r t h i s unexpectedly l a r g e c o n d i t i o n i n g e f f e c t i s a recent r e p o r t by Bond & Harland (1975) of evidence f o r second order c o n d i t i o n i n g e f f e c t s i n a t a s t e a v e r s i o n procedure. They p a i r e d a n e u t r a l t a s t e with a p r e v i o u s l y c o n d i t i o n e d a v e r s i v e s o l u t i o n i n j e c t e d i n t o the r a t s ' mouths. Rats exposed to the second order c o n d i t i o n i n g procedure p r e f e r r e d the p r e v i o u s l y n e u t r a l t a s t e stimulus to a l e s s e r degree than a p p r o p r i a t e c o n t r o l r a t s . One c o u l d argue from these r e s u l t s t h a t the s u b s t a n t i a l c o n d i t i o n i n g of avoidance of the added t a s t e shown i n the present s e r i e s of experiments i s due to a normal c o n d i t i o n i n g e f f e c t (added t a s t e - L i C l a s s o c i a t i o n ) p l u s a second order (added t a s t e - a v e r s i v e t a s t e a s s o c i a t i o n ) c o n d i t i o n i n g e f f e c t . One could a l s o p o s t u l a t e a s u r v i v a l mechanism t h a t would account f o r the l a r g e amount of c o n d i t i o n i n g to the added s t i m u l u s . When the r a t has been poisoned once and then subseguently experiences t h a t poison aga i n , o n l y now combined with a new t a s t e element, the r a t may adopt the r u l e : t a s t e element x l e a d s to p o i s o n , what about t a s t e element y (the new t a s t e element)? T h i s would l e a d t o an enhanced a t t e n t i o n (or s a l i e n c e ) to the new (added) t a s t e element which should i n c r e a s e 116 i t s c o n d i t i o n a b i l i t y ( E e s c o r l a & Wagner, 1972). Along these l i n e s LoLordo, Jacobs, & Foree (1976) have r e c e n t l y r e p o r t e d data from pigeons showing that b l o c k i n g does not occur when the added element i s " r e l e v a n t " ( l i g h t i n an a p p e t i t i v e t a sk, see Foree 6 LoLordo, 1973). LoLordo e t a l . (1976) used pigeons i n an a p p e t i t i v e b l o c k i n g procedure with l i g h t and tone. They found t h a t p r e t r a i n i n g with tone d i d not r e s u l t i n subseguent b l o c k i n g of c o n t r o l by l i g h t when added i n compound to the tone. C o n v e r s e l y , when responding was f i r s t c o n d i t i o n e d t o the l i g h t , the tone a c q u i r e d almost no c o n t r o l over behavior. I t may be t h a t a l l t a s t e s are " r e l e v a n t " t o the r a t . The r e s u l t s of Experiments IA and IB support such a n o t i o n . When a compound was f o l l o w e d by i l l n e s s the r a t s avoided both component elements. Thus, r a t s a p p a r e n t l y " a t t e n d " to a l l t a s t e s . Such would seeminqly operate a g a i n s t b l o c k i n g a c c o r d i n g t o LoLordo e t a i i s . a n a l y s i s . The use of more a r b i t r a r y s t i m u l i such as tones and l i g h t s used by Kamin and others may allow b l o c k i n g to occur i n the r a t . The data f o r the remaining groups support the r e s u l t s o b t a i n e d with Groups 1 and 2. Group 4 showed that preexposing both t a s t e elements r e s u l t s i n l e s s i n t a k e of the added t a s t e s o l u t i o n r e l a t i v e to the Compound and the s o l u t i o n f i r s t p a i r e d with i l l n e s s . These r e s u l t s are r e a d i l y p r e d i c t a b l e . Both t a s t e s o l u t i o n s were preexposed once,, thus r e s u l t i n g i n an increment of " l e a r n e d s a f e t y " o r a t l e a s t " l e a r n e d i r r e l e v a n c e " . Avoidance o f each s o l u t i o n would thus be expected to be c o n d i t i o n e d slower when p a i r e d with t o x i c o s i s . Thus, NaCl avoidance would be 117 p r e d i c t e d to be c o n d i t i o n e d to a l e s s e r degree- T h i s d i d happen-H h i l e the r e s u l t s of Group 4 c l e a r l y show that c o n d i t i o n i n g of NaCl avoidance can be a t t enuated, i t does not argue f o r an acceptance of a b l o c k i n g i n t e r p r e t a t i o n - In order t o apply the b l o c k i n g i n t e r p r e t a t i o n i t would be necessary t o p a i r the Compound with t o x i c o s i s s e v e r a l times ( t h i s was the procedure f o r Group 7). I f NaCl i n t a k e s t i l l remained high then one could argue s t r o n g l y f o r a b l o c k i n g i n t e r p r e t a t i o n . The r e s u l t s of Group 5 showed that even i f the f i r s t s o l u t i o n was p a i r e d with t o x i c o s i s t h r e e times there was s t i l l no i n d i c a t i o n of an impairment of c o n d i t i o n i n g of avoidance of the added s o l u t i o n . In f a c t , NaCl i n t a k e was reduced to l e v e l s o btained when NaCl only i s f o l l o w e d by L i C l . The r e l a t i v e l y high consumption of the novel s o l u t i o n , Vinegar, du r i n g t e s t i n g r u l e s out a g e n e r a l neophobic r e a c t i o n - A l s o suppression to the added s o l u t i o n i n a l l of t h e present experiments cannot be accounted f o r i n terms of a g e n e r a l i z a t i o n e f f e c t ( i . e . , S a c c h a r i n and NaCl are s i m i l a r i n t a s t e ) . Besides the evidence t h a t sweet and s a l t y are q u a l i t a t i v e l y d i f f e r e n t ( E r i c k s o n , et a l . , 1966; Bekesy, 1966), the r e s u l t s of an experiment c a r r i e d out a t the beginning of the present r e s e a r c h shows the l a c k of g e n e r a l i z a t i o n between NaCl and S a c c h a r i n . Six r a t s were given a S a c c h a r i n - L i C l p a i r i n g and t e s t e d two days l a t e r f o r NaCl avoidance. The group consumed a normal amount o f NaCl, thus showing no evidence o f a g e n e r a l i z a t i o n e f f e c t . The r e v e r s e experiment ( N a C l - L i C l , t e s t Saccharin) showed a s i m i l a r l a c k of g e n e r a l i z a t i o n -118 The r e s u l t s of Group 6 were not e n t i r e l y c o n c l u s i v e . For f o u r of s i x r a t s (three males and one female) no evidence of b l o c k i n g was found. Intake of the added s o l u t i o n f o r these four r a t s was 0.1 ml. However, two females showed evidence of b l o c k i n g , consuming 13 and 10 ml of the s o l u t i o n . Thus, the r e s u l t s are somewhat e q u i v o c a l , and because o f the lower dose of L i C l used, d i f f i c u l t to i n t e r p r e t . Again i t should be noted t h a t the i n t a k e of the novel s o l u t i o n . Vinegar, during t e s t i n g supports a s p e c i f i c i t y of c o n d i t i o n i n g i n t e r p r e t a t i o n of the r e s u l t s . The r e s u l t s of Group 7 add s t r e n g t h to the argument t h a t b l o c k i n g i n t a s t e a v e r s i o n l e a r n i n g i s d i f f i c u l t to o b t a i n . Every r a t of Group 7 showed complete avoidance of the added s o l u t i o n (NaCl or Saccharin) d e s p i t e i t s e x t e n s i v e preexposure. Preexposure of a t a s t e s o l u t i o n has o f t e n been shown to r e t a r d l a t e r c o n d i t i o n i n g (Kalat S Rozin, 1973; Fenwick, e t a l . , 1975; as w e l l as s e v e r a l experiments i n the present s e r i e s ) . T h i s f a c t , plus the s m a l l e r c o n d i t i o n i n g e f f e c t when a t a s t e element i s r e i n f o r c e d i n compound (Experiments IA S I B ) , make the present l a c k of a b l o c k i n g e f f e c t even more s u r p r i s i n g . Taken together the r e s u l t s of Experiment VI c o n t r i b u t e s i g n i f i c a n t l y to the b l o c k i n g l i t e r a t u r e . B l o c k i n g i n the g u s t a t o r y system does not (under the c o n d i t i o n s of the present s e r i e s of experiments) occur even i f avoidance of the f i r s t s t i m u l u s i s h i g h l y o v e r t r a i n e d and q u i t e o b v i o u s l y at asymptotic l e v e l s (Group 5). In f a c t , avoidance of the added element i s w e l l c o n d i t i o n e d . B e s c o r l a & Wagner (1972) account f o r b l o c k i n g 119 by suggesting t h a t a given UCS w i l l support o n l y so much c o n d i t i o n i n g . Thus, i f one s t i m u l u s i s already w e l l c o n d i t i o n e d p r i o r t o compounding with another, the added (or redundant) s t i m u l u s w i l l show l i t t l e evidence of c o n d i t i o n i n g because the s t i m u l u s compound i s a l r e a d y near asymptotic c o n d i t i o n i n g l e v e l s . The r e s u l t s of Group 4 apparently c o n t r a d i c t t h i s p o s i t i o n . S a c c h a r i n avoidance was o b v i o u s l y a t very high l e v e l s and yet j u s t one Compound-LiCl t r i a l was s u f f i c i e n t to i n s u r e a dramatic decrease i n NaCl consumption. Thus, although avoidance of S a c c h a r i n was at asymptotic l e v e l s the a d d i t i o n of a redundant t a s t e s t i l l r e s u l t e d i n a powerful c o n d i t i o n i n g e f f e c t . T h i s c o n c l u s i o n i s a l s o supported by the r e s u l t s of Groups 6 and 7. Kamin (1969), suggested a d i f f e r e n t e x p l a n a t i o n of b l o c k i n g . He suggested that l e a r n i n g occurs o n l y when a UCS i s u n p r e d i c t e d or " s u r p r i s i n g " . In the b l o c k i n g procedure, the UCS a f t e r the compound i s not " s u r p r i s i n g " ; being p r e d i c t e d by the f i r s t s t i m u l u s . Kamin t h e r e f o r e suggested that c o n d i t i o n i n g can indeed occur t o the added s t i m u l u s , but doesn't because of i t s redundancy- Kamin showed c o n d i t i o n i n g to the added s t i m u l u s does occur on the f i r s t compound c o n d i t i o n i n g t r i a l , but not on succeeding t r i a l s (because the added stimulus i s now redundant to UCS p r e d i c t i o n ) - I t f o l l o w s from the redundancy notion of Kamin»s, i f the added sti m u l u s i s not redundant, i . e . , p r e d i c t s something new, t h a t c o n d i t i o n i n g w i l l occur. Kamin showed t h a t an e x t r a UCS p r e s e n t a t i o n or a change i n UCS i n t e n s i t y f o l l o w i n g one compound-UCS p a i r i n g e l i m i n a t e d the b l o c k i n g e f f e c t (see a l s o Gray 6 Appignanesi, 1973). I f the i n t e r o c e p t i v e e f f e c t s of 120 L i C l change with s u c c e s s i v e a d m i n i s t r a t i o n s , then the compound-L i C l p a i r i n g ( f o l l o w i n g a s i n g l e e l e m e n t - L i C l p a i r i n g ) should r e s u l t i n c o n d i t i o n i n g to the added element. I t i s d o u b t f u l i f t h i s e x p l a n a t i o n can account f o r the r e s u l t s of Groups 5 and 6. Group 5 r e c e i v e d t h r e e p r i o r s o l u t i o n - L i C l p a i r i n g s , thus making i t u n l i k e l y that the f o u r t h (Compound-LiCl) would be s u b s t a n t i a l l y d i f f e r e n t from the previous t h r e e . T h i s same rea s o n i n g can a l s o be a p p l i e d to the r e s u l t s of Group 6. Mackintosh (1975 a,b) has r e c e n t l y put f o r t h a theory somewhat l i k e t h a t of Kamin which a l s o e x p l a i n s a t l e a s t part of the present r e s u l t s . Mackintosh used a tone, a l i g h t , and an e l e c t r i c shock i n a c o n d i t i o n e d s u p p r e s s i o n of l i c k i n g procedure. He has shown, that a s u b s t a n t i a l amount of c o n d i t i o n i n g does occur to the added stimulus ( f o l l o w i n g p r e c o n d i t i o n i n g with another stimulus) on the f i r s t compound c o n d i t i o n i n g t r i a l . Mackintosh p o i n t s out t h a t c o n d i t i o n i n g to the added'stimulus appears to be r e s t r i c t e d t o the f i r s t c o n d i t i o n i n g t r i a l . Mackintosh b e l i e v e s t h a t b l o c k i n g i s due to the animals' l e a r n i n g to ignore the added element once they have l e a r n e d t h a t i t i s redundant. Part of the r e s u l t s of Groups 1, 2, 4, and 5 (except f o r the complete suppression of i n t a k e of the added s o l u t i o n ) f i t i n t o t h i s f o r m u l a t i o n - Because, the degree of c o n d i t i o n i n g i s u s u a l l y l a r g e a f t e r one t r i a l i n t a s t e a v e r s i o n l e a r n i n g , one would p r e d i c t that the f i r s t Compound t r i a l would r e s u l t i n a s u b s t a n t i a l amount of c o n d i t i o n i n g of avoidance of the added t a s t e element- T h i s i n f a c t o c c u r r e d . The r e s u l t s of Groups 6 and 7 do not f i t as w e l l i n t o 121 Mackintosh's f o r m u l a t i o n . Because of the low dose of L i C l (Group 6) or the e x t e n s i v e preexposure (Group 7), one would p r e d i c t much l e s s c o n d i t i o n i n g t o the added or redundant t a s t e on the f i r s t c o n d i t i o n i n g t r i a l . Repeated Compound-LiCl p a i r i n g s should r e s u l t i n no more c o n d i t i o n i n g to the added s t i m u l u s element than that produced on the f i r s t p a i r i n g . T h i s o b v i o u s l y d i d not occur i n f o u r of s i x r a t s of Group 6 or any r a t s of Group 7. I t may be t h a t the r a t r e q u i r e s numerous t r i a l s before t a s t e redundancy can be l e a r n e d ; however, by t h i s time complete c o n d i t i o n i n g to the added s t i m u l u s has already o c c u r r e d . The s u b s t a n t i a l c o n d i t i o n i n g o f avoidance of the added t a s t e seen i n Groups 1 and 2 r e l a t i v e t o Group 3 i s not as e a s i l y accounted f o r i n Mackintosh's f o r m u l a t i o n , u n l e s s one p o s i t s i n a d d i t i o n a strong second order c o n d i t i o n i n g e f f e c t , or the n o t i o n t h a t the l e a r n i n g r a t e parameter i s t e m p o r a r i l y i n c r e a s e d on the f i r s t compound t r i a l due to the added element being i n a known c o n d i t i o n i n g s i t u a t i o n . The l a c k of b l o c k i n g i n the present experiment can be a t t r i b u t e d t o at l e a s t two c l a s s e s of events. The simple lack of b l o c k i n g i s e a s i l y p r e d i c t e d by Mackintosh (1975a,b; see a l s o McHose S Moor, 1976). C o n d i t i o n i n g occurs t o the added sti m u l u s because the r a t has not l e a r n e d t h a t i t i s redundant. The unexpectedly l a r g e amount of c o n d i t i o n i n g t o the added sti m u l u s shown by Groups 1 and 2 (as w e l l as Groups 5, 6, and 7) can be accounted f o r by a combination of f a c t o r s , i n c l u d i n g : second order c o n d i t i o n i n g (Bond & Harland, 1976), s t i m u l u s - s t i m u l u s a s s o c i a t i o n s (Lavin, 1976), and cue-conseguence r e l e v a n c e 122 (Revusky S G a r c i a , 1973; Shettleworth, 1972; LoLordo et a l . , 1976); a l l of which c o n t r i b u t e to the i n c r e a s e d s a l i e n c e of the added s o l u t i o n . 123 GENERAL SUMMARY AND DISCUSSION In the I n t r o d u c t i o n , s e v e r a l g o a l s were o u t l i n e d - F i r s t of a l l , i t was hoped t h a t the b a s i c technigue of mixing t a s t e s o l u t i o n s would prove u s e f u l i n the i n v e s t i g a t i o n of compound s t i m u l u s c o n t r o l - The r e s u l t s of Experiments I through VI demonstrate the p o t e n t i a l u s e f u l n e s s of such a technigue. The second goal was to provide some p r e l i m i n a r y i n f o r m a t i o n on c e r t a i n aspects of t r a d i t i o n a l c o n d i t i o n i n g phenomena- T h i s was accomplished by demonstrating c o n t r o l both by the elements of a c o n d i t i o n e d compound and by a compound of s e p a r a t e l y c o n d i t i o n e d elements- A l s o , work was presented concerning s t i m u l u s i n t e r a c t i o n s w i t h i n a compound (Experiments I I I & IV) as w e l l as work on overshadowing and b l o c k i n g - I t i s e v i d e n t t h a t many aspects of compound s t i m u l u s c o n t r o l can be i n v e s t i g a t e d using a m i x e d - s o l u t i o n - g u s t a t o r y - m a l a i s e technigue of i n v e s t i g a t i o n . The t h i r d g o a l (perhaps the most important) concerns t,he d e l i n e a t i o n of the g u s t a t o r y - m a l a i s e system as a c o n d i t i o n a b l e cue-conseguence system s i m i l a r to other more commonly s t u d i e d cue-conseguence systems. As pointed out i n the I n t r o d u c t i o n , the ge n e r a l unigueness of the t a s t e a v e r s i o n phenomenon i s p r e s e n t l y i n d i s p u t e (see G a r c i a , Hawkins, 6 Rusinak, 1976, and Bitterman, 1976). The present r e s e a r c h i n g e n e r a l provides a d d i t i o n a l evidence of s i m i l a r i t i e s between t a s t e a v e r s i o n l e a r n i n g and more t r a d i t i o n a l cue-conseguence l e a r n i n g . Experiment IA and IB showed t h a t c o n d i t i o n i n g of avoidance o f the elemnts of a compound gus t a t o r y s t i m u l u s can occur i n ways s i m i l a r to t h a t i n 124 other cue-consequence systems. These r e s u l t s along with those of Experiment I I (showing avoidance of a t a s t e compound made up of s e p a r a t e l y c o n d i t i o n e d elements) f i t i n very well with t r a d i t i o n a l f o r m u l a t i o n s of other cue-consequence l e a r n i n g systems (Weiss, 1972), Some evidence of " c o n f i g u r i n g " (Razran, 1965; R e s c o r l a , 1972) was found, and suggests t h a t the gustatory system i s capable of a higher order o f stimulus p r o c e s s i n g than suggested by a " p r i m i t i v e systems" approach. The r e s u l t s of Experiments I I I and IV were a l s o e a s i l y i n t e g r a t e d i n t o more t r a d i t i o n a l cue-conseguence l e a r n i n g e x p l a n a t i o n s . Experiment I I I showed that i f a f a m i l i a r (safe) t a s t e s o l u t i o n i s put i n compound with a novel s o l u t i o n and the compound i s then f o l l o w e d by t o x i c o s i s , then most or a l l of the c o n d i t i o n e d avoidance of the compound can be accounted f o r i n terms of avoidance of the novel t a s t e s o l u t i o n . T h i s i s c o n s i s t e n t with s i m i l a r e f f e c t s i n t r a d i t i o n a l l e a r n i n g paradigms (Revusky, 1971; R e s c o r l a S Wagner, 1972). Experiment IV demonstrated that averaging (Weiss, 1972) w i l l occur i n the g u s t a t o r y system when a f a m i l a r (safe) t a s t e s o l u t i o n i s compounded with an unsafe s o l u t i o n - These r e s u l t s a l s o meshed with the t r a d i t i o n a l c o n d i t i o n e d and l a t e n t i n h i b i t i o n l i t e r a t u r e (Hearst, 1972)-Experiment V demonstrated overshadowing i n the g u s t a t o r y -malaise system, but f a i l e d t o show a symmetrical e f f e c t , i . e . . S a c c h a r i n overshadowed NaCl, but the r e v e r s e was not obt a i n e d . P o s s i b l e e x p l a n a t i o n s , such as n o v e l t y and innate sodium a p p e t i t e , were d i s c u s s e d , but such asymmetry i s not uncommon i n 125 o t h e r cue-conseguence systems (Baron, 1965). The r e s u l t s of Experiment VI on b l o c k i n g proved to be the most d i f f i c u l t t o f i t i n t o a t r a d i t i o n a l cue-conseguence f o r m u l a t i o n . F o l l o w i n g one t a s t e stimulus with t o x i c o s i s , and then compounding t h a t s t i m u l u s with another n o v e l s t i m u l u s , and f o l l o w i n g t h a t compound with t o x i c o s i s should r e s u l t i n an a t t e n u a t i o n of c o n d i t i o n i n g t o the added s t i m u l u s element (Kamin, 1968, 1969; Revusky, 1971). T h i s was c l e a r l y not the case. In f a c t an enhancement of c o n d i t i o n i n g of avoidance o f the added element was demonstrated. T h i s may be due to a fundamental d i f f e r e n c e i n the g u s t a t o r y - m a l a i s e l e a r n i n g system as c o n t r a s t e d to other cue-conseguence systems ( G a r c i a , McGowan, & Green, 1972; Rozin S K a l a t , 1971). However, as Bitterman (1976) has r e c e n t l y pointed out, c o n c l u s i o n s should be based on e x t e n s i v e i n v e s t i g a t i o n of the fundamental r e l a t i o n s governing a p a r t i c u l a r phenomenon before any apparent unigue p r o p e r t i e s are emphasized. A l s o , the r e c e n t experimental r e s u l t s of LoLordo e t a l . (1976) and t h e o r e t i c a l n o t i o n s of Kamin (1969) and Mackintosh (1975b) suggest p o s s i b l e reasons f o r the f a i l u r e to o b t a i n b l o c k i n g and suggests c o n d i t i o n s under which b l o c k i n g would not occur i n t r a d i t i o n a l cue-avoidance l e a r n i n g . I t i s i n t e r e s t i n g n e v e r t h e l e s s to s p e c u l a t e on the unigue a d a p t i v e s i g n i f i c a n c e of g u s t a t o r y - m a l a i s e l e a r n i n g . The r a t as B a r n e t t (1963) has p o i n t e d out i s h i g h l y adapted to i t s environment. The r a t s ' g u s t a t o r y system i s very important f o r i t s s u r v i v a l (Rozin & K a l a t , 1971), and i t would not be s u r p r i s i n g i f c e r t a i n mechanisms had evolved to i n s u r e a c l o s e 126 a s s o c i a t i o n between g u s t a t o r y s t i m u l a t i o n and s i c k n e s s (Garcia e t a l - / 1974)- Many people have argued f o r the e x i s t e n c e of such mechanisms i n animals (e.<j-, s h e t t l e w o r t h , 1972; Seligman S Hager, 1972). The r e s u l t s of Experiment VI, as well as those of K a l a t and Rozin (1972), suggest t h a t a l e a r n i n g phenomenon as fundamental as b l o c k i n g (see W i l l i a m s , 1975) may not be e a s i l y demonstrable i n the g u s t a t o r y system of the r a t . 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J o u r n a l of the Experimental A n a l y s i s of Behavior, 1973, 20, 209-218. 138 APPENDIX A S t a t i s t i c a l R e s u l t s f o r Experiment I A X Group 1_ Pre- and p o s t - c o n d i t i o n i n g comparisons o f f l u i d i n t a k e , e. ,<j- , pre-NaCl i n t a k e compared t o t e s t t r i a l 1 NaCl i n t a k e has a t value of 8.89. A l l comparisons used a repeated measures t t e s t with n-1 degrees of freedom. A l l v a l u e s r e p o r t e d are s i g n i f i c a n t a t the 0.05 l e v e l or g r e a t e r (** s i g n i f i e s n o n s i g n i f i c a n t r e s u l t s ) . P o s t - c o n d i t i o n i n g t e s t t r i a l 1 2 3 Pre-NaCl P r e - S a c c h a r i n Pre-Compound Pre-Vinegar 8. 89 4. 58 8. 59 3-98 ** 5.75 3.42 ** 3.57 A l l p o s s i b l e p a i r w i s e comparisons of f l u i d i n t a k e f o r the f i r s t , second, and t h i r d t e s t c y c l e s . Small numbers to the upper l e f t of each q value i n d i c a t e s t e s t t r i a l . A l l comparisons were made with Tukey's HSD t e s t with 15 degrees of freedom and the a p p r o p r i a t e mean sguare r e s i d u a l as the e r r o r term. A l l values r e p o r t e d are s i g n i f i c a n t at the 0.05 l e v e l or g r e a t e r (** s i g n i f i e s n o n s i g n i f i c a n t r e s u l t s ) . S accharin Compound Vinegar 17 .68 1 ** 122.6 5 NaCl 26.31 26 . 6 211.2 3 * * 3 5.65 3 * * 18.8 115.19 S a c c h a r i n 2 9 .7 2** 3 7 .3 123 .7 3 Compound 212.32 3 * * S t a t i s t i c a l R e s u l t s f o r Experiment I A X Group 2 Pre- and p o s t - c o n d i t i o n i n g comparisons of f l u i d i n t ; Experiment IA, Group 1 f o r f u r t h e r e x p l a n a t i o n . P o s t - c o n d i t i o n i n g t e s t t r i a l 1 2 3 Pre-NaCl 5.51 ** ** P r e - S a c c h a r i n 9. 95 5. 13 ** Pre-Compound 11 .47 7.17 7.58 139 A l l p o s s i b l e p a i r w i s e comparison (degrees of freedom, 10). See Experiment IA, Group 1 f o r f u r t h e r e x p l a n a t i o n . Saccharin compound i * * 14.86 NaCl 2** 27.5 3** 312.3 1 *# S a c c h a r i n 2 4 . 3 35.6 S t a t i s t i c a l R e s u l t s f o r Experiment I A X Group 3 Pre- and p o s t - c o n d i t i o n i n g comparisons of f l u i d i n t a k e . See Experiment IA, Group 1 f o r f u r t h e r e x p l a n a t i o n . P o s t - c o n d i t i o n i n g t e s t t r i a l 1 2 3 Pre-Sucrose 5.98 3.54 2.77 Pre-Quinine 7.57 5.64 5.24 Pre-Compound 10.35 7.23 5.85 Pre-NaCl ** ** ** A l l p o s s i b l e p a i r w i s e comparisons (degrees of freedom, 15). See Experiment IA, Group 1 f o r f u r t h e r e x p l a n a t i o n . Quinine Compound M C I 1** 1 ** 19.94 Sucrose 2** 2** 24.45 3 * * 34.73 3 * * 1 ** 110.14 Quinine 2 6. 53 28.6 3 5. 87 35.25 M2.35 Compound 18.3 (3 36.2 140 S t a t i s t i c a l R e s u l t s f o r Experiment I A X Group 4 Pre- and p o s t - c o n d i t i o n i n g comparisons o f f l u i d i n t a k e . See Experiment IA, Group 1 f o r f u r t h e r e x p l a n a t i o n . P o s t - c o n d i t i o n i n g t e s t t r i a l 1 2 3 Pre-Sucrose 16.96 10. 98 6.26 Pre-Quinine 7.23 4.24 ** Pre-Compound 15.64 12-99 9.18 Pre-NaCl ** ** ** A l l p o s s i b l e p a i r w i s e comparisons (degrees of freedom, 15). See Experiment IA, Group 1 f o r f u r t h e r e x p l a n a t i o n . Quinine Compound l a C l I * * M3.58 Sucrose 27-56 2** 28.32 34.35 3** 35.73 1 * * M0.98 Quinine 2 7.83 25.32 3 5. 83 35.01 M4.5 Compound 214.78 310.07 S t a t i s t i c a l R e s u l t s f o r Experiment Group X Pre- and p o s t - c o n d i t i o n i n g comparisons o f f l u i d i n t a k e . Each s o l u t i o n i n t a k e during t e s t i n g was compared with c o n d i t i o n i n g day i n t a k e of the Compound. A l l comparisons were made with Tukey's HSD t e s t (degrees of freedom, 21). A l l re p o r t e d g values are s i g n i f i c a n t at the 0.05 l e v e l or better. P o s t - c o n d i t i o n i n g t e s t t r i a l 1 2 3 NaCl vs pre-Compound 5.83 ** ** Sac c h a r i n vs pre-Compound 6.14 ** ** Compound vs pre-Compound 11.25 5.32 4. 22 141 A l l p o s s i b l e p a i r w i s e comparisons. See Experiment IA, Group 1 f o r f u r t h e r e x p l a n a t i o n s . Saccharin Compound i * * 15.41 NaCl 2 * * 27 . 31 3 * * 38.21 15. 11 Sa c c h a r i n 26,31 3 6.93 S t a t i s t i c a l R e s u l t s f o r Experiment I B x Group 2 Pre- and p o s t - c o n d i t i o n i n g comparisons of f l u i d i n t a k e {degrees of freedom, 15). See Experiment IB, Group 1 f o r f u r t h e r e x p l a n a t i o n . P o s t - c o n d i t i o n i n g t e s t t r i a l 1 2 3 Quinine ys pre-Compound 21.0 4.32 4.25 Sucrose ys pre-Compound 28.34 8.62 ** Compound _vs pre-Compound 28.58 13.21 ** A l l p o s s i b l e p a i r w i s e comparisons. See Experiment IA, Group 1 f o r f u r t h e r e x p l a n a t i o n . Sucrose Compound i 7.17 17.32 Quinine 2 * * 2 4.33 3 * * Sucrose 2 * * 3 # * 142 S t a t i s t i c a l R e s u l t s f o r Experiment I B X Group 3 Pre- and p o s t - c o n d i t i o n i n g comparisons of f l u i d i n t a k e -Each s o l u t i o n i n t a k e during t e s t i n g was compared with c o n d i t i o n i n g day i n t a k e of Vinegar (degrees of freedom, 20). See Experiment IB, Group 1 f o r f u r t h e r e x p l a n a t i o n . PP.st-cgnditioning t e s t t r i a l 1 2 3 NaCl ys pre-Vinegar ** ** ** S a c c h a r i n ys pre-Vinegar ** ** ** Compound ys pre-Vinegar ** ** ** Vinegar ys pre-Vinegar 6.68 4.67 4.43 A l l p o s s i b l e p a i r w i s e comparisons. See Experiment IA, Group 1 f o r f u r t h e r e x p l a n a t i o n . Saccharin Compound Vinegar not not NaCl computed computed 13.75 not S a c c h a r i n computed 5.71 Compound 9.31 S t a t i s t i c a l R e s u l t s f o r Experiment I I X Group 1 Pre- and p o s t - c o n d i t i o n i n g comparisons of f l u i d i n t a k e . See Experiment IA, Group 1 f o r f u r t h e r e x p l a n a t i o n . A l l comparisons were made with Tukey's HSD t e s t (degrees of freedom, 20). P o s t - c o n d i t i o n i n g t e s t t r i a l 1 2 3 Pre-NaCl 19.6 5.62 ** Pre - S a c c h a r i n 10-4 ** ** Pre-NaCl y s Compound ~ 21.0 13.23 ** P r e - s a c c h a r i n ys Compound 10.3 ** ** 143 Pairwise comparisons f o r Compound vs NaCl and S a c c h a r i n d u r i n g f i r s t three t e s t c y c l e s . See Experiment IA, Group 1 f o r f u r t h e r e x p l a n a t i o n . S a c c h a r i n NaCl Compound 24 .72 24.53 35,07 a * * S t a t i s t i c a l R e s u l t s f o r Experiment I I X Group 2 Pre- and p o s t - c o n d i t i o n i n g comparisons o f f l u i d i n t a k e (degrees of freedom, 16) . See Experiment II., Group 1 f o r f u r t h e r e x p l a n a t i o n . P o s t - c o n d i t i o n i n g t e s t t r i a l 1 2 3 Pre-NaCl 9.33 ** ** Pre - S a c c h a r i n 5.33 ** ** Pre-NaCl ys Compound ~ 13.41 10.21 ** Pre - S a c c h a r i n ys Compound 6.5 ** ** Pairwise comparisons f o r Compound ys NaCl and Sac c h a r i n d u r i n g the f i r s t t h ree t e s t c y c l e s . See Experiment IA, Group 1 f o r f u r t h e r e x p l a n a t i o n . S a c c h a r i n NaCl 1** 1** Compound 2 * * 29.36 3** 35.-j S t a t i s t i c a l R e s u l t s f o r Experiment I I X Group 3 Pre- and p o s t - c o n d i t i o n i n g comparisons of f l u i d i n t ake (degrees of freedom, 25). See Experiment I I , Group 1 f o r f u r t h e r e x p l a n a t i o n . P o s t - c o n d i t i o n i n g t e s t t r i a l 1 2 3 Pre-NaCl 25.86 4.57 ** Pre - S a c c h a r i n 18.11 6.32 4-75 not not Pre-Vinegar ** computed computed 144 Pre-NaCl ys Compound 26.11 Pr e - S a c c h a r i n ys Compound 18.25 12.32 4.63 ** Pairwise comparisons f o r s o l u t i o n s shown. See Experiment IA, Group 1 f o r f u r t h e r e x p l a n a t i o n . Compound Vinegar S a c c h a r i n 2 * * 3 * * l a C l i * * 25. 13 3** Compound 120.6 120.37 320.75 S t a t i s t i c a l R e s u l t s f o r Experiment I I X Group 4 Pre- and p o s t - c o n d i t i o n i n g comparisons o f f l u i d i n t a k e (degrees of freedom, 25). See Experiment I I , Group 1 f o r f u r t h e r e x p l a n a t i o n . P o s t - c o n d i t i o n i n g t e s t t r i a l Pre-Vinegar P r e - C o f f e e Pre-Vinegar ys Compound Pr e - C o f f e e ys Compound Pre-Vinegar y s NaCl+Saccharin Pre-Coffee ys NaCl+Saccharin 1 13.32 15.02 13.6 17.62 ** 5.98 2 9.32 7.13 11. 13 14.31 ** 3 7. 31 ** 5.26 6. 42 not computed not computed Pairwi s e comparisons f o r s o l u t i o n s shown. See Experiment IA, Group 1 f o r f u r t h e r e x p l a n a t i o n . Vinegar Compound NaCl + S a c c h a r i n 1** 2 * * 3 * * 113.6 Co f f e e i * * 2 * * 3 4. 73 18.31 Compound 1 1 5 . 0 2 145 S t a t i s t i c a l R e s u l t s f o r Experiment I I I x Group 1 Pre- and p o s t - c o n d i t i o n i n g comparisons of f l u i d i n t a k e (degrees of freedom, 15). See Experiment IB, Group 1 f o r f u r t h e r e x p l a n a t i o n . Pre- ys post-NaCl used a repeated measures t t e s t . P o s t - c o n d i t i o n i n g t e s t t r i a l NaCl ys pre-NaCl t=2.64 ** ** S a c c h a r i n ys pre-Compound 6.23 ** ** Compound vs pre- Compound 7.09 ** ** A l l p o s s i b l e p a i r w i s e comparisons. See Experiment IA, Group 1 f o r f u r t h e r e x p l a n a t i o n . S a c c h a r i n Compound M1.0 110. 8 NaCl 24.12 2^,63 3 n o t 3 n o t computed computed i ** S a c c h a r i n 2 * * 3 * * S t a t i s t i c a l R e s u l t s f o r Experiment I V X Group 1 Pre- and p o s t - c o n d i t i o n i n g comparisons of f l u i d i n t a k e (degrees of freedom, 15). See Experiment IB, Group 1 f o r f u r t h e r e x p l a n a t i o n . P p s t 7 c o n d i t i o n i n q t e s t t r i a l 1 2 3 NaCl ys pre-NaCl ** ** ** Compound ys pr e - S a c c h a r i n ** ** ** S a c c h a r i n y s pr e - S a c c h a r i n 6.38 ** ** 146 A l l p o s s i b l e p a i r w i s e comparisons. See Experiment IA, Group 1 f o r f u r t h e r e x p l a n a t i o n . Compound Sac c h a r i n M3.25 M2.25 NaCl 2 * * 27.33 3 n o t 3 n o t computed computed 1 ** Compound 24.27 3 * * S t a t i s t i c a l R e s u l t s f o r Experiment I V X Group 2 Pre- and p o s t - c o n d i t i o n i n g comparisons o f f l u i d i n t a k e {degrees of freedom, 15). See Experiment IB, Group 1 f o r f u r t h e r e x p l a n a t i o n . P o s t - c o n d i t i o a i n g t e s t t r i a l 1 2 3 Sa c c h a r i n ys not pre - S a c c h a r i n ** ** computed NaCl ys pre-NaCl 13.42 13.42 10.11 A l l p o s s i b l e p a i r w i s e comparisons. See Experiment IA, Group 1 f o r f u r t h e r e x p l a n a t i o n . Compound NaCl 17.89 M2.0 Sa c c h a r i n 24.13 26.63 3 * * 3 n o t computed Compound 14. 10 24. 29 3 * * 147 S t a t i s t i c a l R e s u l t s f o r Experiment V x Group jl Pre- and p o s t - c o n d i t i o n i n g comparisons of f l u i d i n t a k e (degrees of freedom, 15). See Experiment IB, Group 1 f o r f u r t h e r e x p l a n a t i o n . P o s t - c o n d i t i o n i n g t e s t t r i a l 1 2 3 NaCl ys pre-Compound ** ** ** S a c c h a r i n ys pre-Compound 5.15 ** ** Compound ys pre-Compound 6.15 ** ** A l l p o s s i b l e p a i r w i s e comparisons. See Experiment IA, Group 1 f o r f u r t h e r e x p l a n a t i o n . Saccharin Compound 17.26 18.26 NaCl 2 4.63 25.22 3 * * 3 * * 1 ** S a c c h a r i n 2 * * 3 * * S t a t i s t i c a l R e s u l t s f o r Experiment V x Group 2 Sel e c t e d p a i r w i s e comparisons o n l y . A l l comparisons used repeated measures t t e s t s . See Experiment IA, Group 1 f o r f u r t h e r e x p l a n a t i o n . S a c c h a r i n Compound 17.81 26.71 33.52 148 S t a t i s t i c a l R e s u l t s f o r Experiment V x Group 3 Pre- and p o s t - c o n d i t i o n i n g comparisons of f l u i d i n t a k e (degrees of freedom, 15). See Experiment IB, Group 1 f o r f u r t h e r e x p l a n a t i o n . Po s t - c on d i t i o n i n g t e s t t r i a l 1 2 NaCl ys pre-Compound 4.77 ** Sa c c h a r i n ys pre-Compound 4.17 ** Compound js pre-Compound 7.84 ** a l l p o s s i b l e p a i r w i s e comparisons. See Experiment IA, Group 1 f o r f u r t h e r e x p l a n a t i o n . S a c c h a r i n Compound NaCl z** 2 * * 3 * * 3 * * 1 * * S a c c h a r i n 2 * * 3 * * S t a t i s t i c a l R e s u l t s f o r Experiment V I X Group 1 Pre- and p o s t - c o n d i t i o n i n g comparisons of f l u i d i n t a k e (degrees of freedom, 15). Each s o l u t i o n i n t a k e during t e s t i n g was compared with c o n d i t i o n i n g day i n t a k e of S a c c h a r i n . See Experiment IB, Group 1 f o r f u r t h e r e x p l a n a t i o n . R P § £, ~ £ SB &i £ i Q.P I £3 Mjt t r i a l 1 2 3 NaCl ys pre - S a c c h a r i n 15.48 5.73 ** S a c c h a r i n ys pre- Saccharin 15.24 10. 23 6. 23 Compound ys pr e - S a c c h a r i n 15.58 15-58 15.58 149 A l l p o s s i b l e p a i r w i s e comparisons. See Experiment IA, Group 1 f o r f u r t h e r e x p l a n a t i o n . Saccharin Compound NaCl 2 * * 2 * * 3 * * 3 * * 1 ** Sa c c h a r i n 2 * * 3 * * S t a t i s t i c a l R e s u l t s f o r Experiment V I X Group 2 Pre- and p o s t - c o n d i t i o n i n g comparisons of f l u i d i n t a k e (degrees of freedom, 15). Each s o l u t i o n i n t a k e during t e s t i n g was compared with c o n d i t i o n i n g day intake of S a c c h a r i n . See Experiment IB, Group 1 f o r f u r t h e r e x p l a n a t i o n . P o s t - c o n d i t i o n i n g t e s t t r i a l 1 2 3 NaCl ys pre-NaCl 25.68 16,37 7.25 S a c c h a r i n ys pre-NaCl 24.38 16.21 10.12 Compound ys pre-NaCl 26.31 22.31 17.23 A l l p o s s i b l e p a i r w i s e comparisons. See Experiment IA, Group 1 f o r f u r t h e r e x p l a n a t i o n . S a c c h a r i n Compound NaCl 2 * * 2** 3 * * 3 * * 1 * * S a c c h a r i n 2 * * 3 * * S t a t i s t i c a l R e s u l t s f o r Experiment VT X Group 3 The only r e s u l t s of importance are r e p o r t e d i n the t e x t . 150 S t a t i s t i c a l R e s u l t s f o r Bxperiment VI x Group 4 Pre- and p o s t - c o n d i t i o n i n g comparisons o f f l u i d i n t a k e (degrees of freedom, 15). NaCl and S a c c h a r i n were compared to p r e - c o n d i t i o n i n g l e v e l s , while Compound i n t a k e was compared to p r e - c o n d i t i o n i n g l e v e l s of both s o l u t i o n s . See Experiment IB, Group 1 f o r f u r t h e r e x p l a n a t i o n . P o s t - c o n d i t i o n i n g t e s t t r i a l 1 2 3 Pre-NaCl 4.53 ** ** P r e - S a c c h a r i n 23.17 22.02 20.43 Compound vs pre-NaCl ~ 24.23 23.12 21.04 Compound y s p r e - S a c c h a r i n 22.14 21.13 20.67 A l l p o s s i b l e p a i r w i s e comparisons. See Experiment IA, Group 1 f o r f u r t h e r e x p l a n a t i o n (consumption measures were converted to percent b a s e l i n e l e v e l s ; see Experiment IA i n t e x t ) . Saccharin Compound 14.44 14.54 NaCl 28.73 29.27 319.12 320.73 l * * S a c c h a r i n 2 * * 3 * * S t a t i s t i c a l R e s u l t s f o r Experiment V I X Group 5 Pre- and p o s t - c o n d i t i o n i n g comparisons of f l u i d i n t a k e (degrees of freedom, 20). Each s o l u t i o n i n t a k e during t e s t i n g was compared with the f i r s t c o n d i t i o n i n g day intake of S a c c h a r i n . See Experiment IB, Group 1 f o r f u r t h e r e x p l a n a t i o n . P o s t - c o n d i t i o n i n g t e s t t r i a l 1 2 3 NaCl ys p r e - S a c c h a r i n 12.28 7.23 ** S a c c h a r i n ys pr e - S a c c h a r i n 12.37 12.37 12.37 Vinegar ys not p r e - S a c c h a r i n ** ** computed 151 Compound vs pre - S a c c h a r i n 12.37 12.37 12.25 A l l p o s s i b l e p a i r w i s e comparisons. See Experiment IA, Group 1 f o r f u r t h e r e x p l a n a t i o n . S a c c h a r i n Compound Vinegar i ** MO.89 NaCl 24.35 24.35 29.23 319.73 319.65 3 n o t computed I ** M0.98 Sa c c h a r i n 2** 217.68 3 * * 3 n o t computed MO.98 Compound 2 17.68 3 n o t computed S t a t i s t i c a l R e s u l t s f o r Experiment V I A Group 6 Pre- and p o s t - c o n d i t i o n i n g comparisons o f f l u i d i n t a k e (degrees of freedom, 20). Each s o l u t i o n i n t a k e during t e s t i n g was compared to c o n d i t i o n i n g day int a k e of S a c c h a r i n . See Experiment IB, Group 1 f o r f u r t h e r e x p l a n a t i o n . P o s t - c o n d i t i o n i n g t e s t t r i a l 1 2 3 NaCl vs pre - S a c c h a r i n ** ** ** Sac c h a r i n ys pre - S a c c h a r i n 6-89 6.53 5. 95 Vinegar ys not not pre - S a c c h a r i n ** computed computed Compound y s pr e - S a c c h a r i n 6,93 4.56 A l l p o s s i b l e p a i r w i s e comparisons. See Experiment IA, Group 1 f o r f u r t h e r e x p l a n a t i o n . Saccharin Compound Vinegar i * * *** 15.82 NaCl 2 * * 2** 2 n 0 t computed 312.43 3** 3 n o t computed 152 Sa c c h a r i n i ** 2 * * 3 * * 18.73 2not computed 3 n o t computed Compound 18.57 2 not computed 3 not computed S t a t i s t i c a l R e s u l t s f o r Experiment V I x Group 7 Pre- and p o s t - c o n d i t i o n i n g comparisons of f l u i d i n t a k e (degrees of freedom, 20). Each s o l u t i o n i n t a k e during t e s t i n g was compared with c o n d i t i o n i n g day in t a k e o f the p r e - c o n d i t i o n e d s o l u t i o n (Saccharin o r NaCl f o r d i f f e r e n t subgroups). See Experiment IB, Group 1 f o r f u r t h e r e x p l a n a t i o n . P o s t - c o n d i t i o n i n g t e s t t r i a l 1 2 3 Added s o l u t i o n vs p r e - c o n d i t i o n e d s o l u t i o n 23.17 1 6. 3 5. 2 P r e - c o n d i t i o n e d s o l u t i o n , pre- 23.29 ys post- i n t a k e Compound ys p r e - c o n d i t i o n e d 23.29 s o l u t i o n 21.3 21-47 19.78 13.12 Vinegar ys p r e - c o n d i t i o n e d s o l u t i o n not computed not computed A l l p o s s i b l e p a i r w i s e comparisons- See Experiment IA, Group 1 f o r f u r t h e r e x p l a n a t i o n . Added s o l u t i o n P r e - c o n d i -t i o n e d s o l u t i o n i ** 25.02 3 4. 3 Compound 1 * * 2 5. 33 3 * * Vinegar 11 5. 3 3 2not computed 3 n o t computed P r e - c o n d i t i o n e d s o l u t i o n i ** 2** M5.47 2 n o t computed 3 * * 3 n o t computed 1 1 5 . 3 3 Compound 2 n o t computed 3 n o t computed 

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